Electric motors

ABSTRACT

A stator defines multiple stator poles with associated electrical windings. A rotor includes multiple rotor poles. The rotor is movable with respect to the stator and defines, together with the stator, a nominal gap between the stator poles and the rotor poles. The rotor poles includes a magnetically permeable pole material. The rotor also includes a series of frequency programmable flux channels (FPFCs). Each FPFC includes a conductive loop surrounding an associated rotor pole. The stator and the rotor are arranged such that the electrical windings in the stator induce an excitement current within at least one of the FPFCs during start-up.

TECHNICAL FIELD

This disclosure relates to electric motors and operation of such motors.

BACKGROUND

Two of the ways in which the performance of electric motors may becharacterized is by their torque/force and their output power. Theoutput power of a rotary motor is a product of a torque that a motorgenerates and an angular velocity of its output shaft. For a linearmotor, the output power is a product of linear force and speed.Conventionally, there are two primary means to directly increase themotor performance: (1) by increasing the size of the motor and (2) bycreating a stronger magnetic field within the motor itself. While theultimate size of a motor limits its specific useful applications,increasing the magnetic field to thereby increase the electromagneticforce may be considered as a key to enable greater motor performance andfurther broader applications of motor technology.

SUMMARY

Various aspects of this disclosure feature a motor with frequencyprogrammable flux channels (FPFCs) disposed around passive poles toalter the path of magnetic flux and to reflect flux produced inoperation to provide a greater component of magnetically induced motiveforce aligned with movement direction (to provide useful torque and/orlinear force).

An example implementation of the subject matter describe within thisdisclosure is an electric machine with the following features. A statordefines multiple stator poles with associated electrical windings. Arotor includes multiple rotor poles. The rotor is movable with respectto the stator and defines, together with the stator, a nominal gapbetween the stator poles and the rotor poles. The rotor poles include amagnetically permeable pole material. The rotor also includes a seriesof frequency programmable flux channels (FPFCs). Each FPFC includes aconductive loop surrounding an associated rotor pole.

An example implementation of the subject matter described within thisdisclosure is an electric machine with the following features. A statoris configured to generate a controlled magnetic field. A rotor isconfigured to move with respect to the stator responsive to thecontrolled magnetic field. The rotor defines, together with the stator,a nominal gap between a surface of the rotor and a surface of thestator. The rotor includes a magnetically permeable pole material. Therotor includes a variable magnetomotive force source controllable by thecontrolled magnetic field produced by stator.

An example implementation of the subject matter described within thisdisclosure is a motor control method with the following features. Apulse of magnetizing current is applied over time to a stator coil of astator pole when the stator pole is aligned with a rotor pole across anominal gap. The magnetizing current is configured to charge a magneticfield within the rotor pole through induced coupling. A load currentpulsed over time is applied to the stator coil when rotor pole ispositioned between adjacent stator poles. The load current pulsesstiffen the magnetic field within the rotor pole. The pulsed loadcurrent includes more pulses per increment of time than pulse themagnetizing current.

An example implementation of the subject matter described within thisdisclosure is a motor control method with the following features. Arotor pole of an electric machine is magnetically hardened throughcurrent around the rotor pole. The current is induced by a currentflowing through a stator coil. Motion of the rotor with respect to thestator is induced by an electromotive force produced by the currentflowing through the stator coil and the current flowing around the rotorpole.

An example implementation of the subject matter described within thisdisclosure is a method of starting a three-phase electric motor. Themethod has the following features. Direct current is flowed through astator winding associated with a phase of stator winding for a durationof time. Then, an inverted direct current is pulsed for a secondduration of time through the stator winding associated with the phase.

An example implementation of the subject matter described within thisdisclosure is a method of driving an electric motor. The method havingthe following feature. An average flux of an electric rotor is increasedprimarily through a waveform excitation from a stator.

Implementations previously described can include any, all, or none ofthe following features.

The stator and the rotor are arranged such that the electrical windingsin the stator excite a current within at least one of the FPFCs duringstart-up.

The stator and the rotor are arranged such that the electrical windingsin the stator magnetize at least one of the rotor poles during start-up.

An excitement current of the FPFC is produced by the electrical windingsin the stator during operation.

The conductive loop includes material more conductive than a rotor corematerial.

The conductive loop includes material less magnetically permeable than arotor core material.

Each of the FPFCs do not overlap with an adjacent FPFC.

The conductive loop includes a substantially uniform inductance. Thesubstantially uniform inductance can be in a radial direction.

The conductive loop includes at least one turn of shorted conductivematerial.

The conductive loop includes shorted litz wire.

A thickness of individual conductors within the conductive loop is smallenough for full skin effect penetration for a drive frequency. The drivefrequency can between 0 hertz and 20 hertz. The drive frequency extendsbetween 100 hertz and 2,000 hertz, or in excess of 20,000 hertz.

The conductive loop includes a rectifier in series with two ends of theconductive loop. The rectifier can include a diode. The diode can be ap-n junction diode. The diode can be a Schottky diode. The Schottkydiode can be a silicon carbide diode. The diode can be a gas diode. Thediode can be a Zener diode.

The conductive loop includes a discrete capacitor in series with twoends of the conductive loop. The capacitor can be connected in parallelwith the diode.

The conductive loop includes a logic circuit in series with two ends ofthe conductive loop. The logic circuit can include a transistor. Thetransistor can include a field effect transistor, a dual gate fieldeffect transistor, or a bipolar junction transistor.

The conductive loop is a first conductive loop, each FPFC furthercomprises a second conductive loop the associated rotor pole and anadditional rotor pole adjacent the first rotor pole. The secondconductive loop can include material more conductive than a rotor corematerial. The second conductive loop can include material lessmagnetically permeable than a rotor core material. The first conductiveloop can include a first substantially uniform inductance and the secondconductive loop can include a second substantially uniform inductance.The second substantially uniform inductance can be in a radialdirection. The second substantially uniform inductance can besubstantially similar to the first substantially uniform inductance. Thesecond conductive loop can include at least one turn of shortedconductive material. The second conductive loop can include shorted litzwire. A thickness of individual conductors within the second conductiveloop can be small enough for full skin effect penetration for a drivefrequency. The second conductive loop can surround a third additionalrotor pole adjacent to the first rotor pole. The second conductive loopcan include a logic circuit in series with two ends of the secondconductive loop. The logic circuit can include a transistor. Thetransistor can include a field effect transistor, a dual gate fieldeffect transistor, or a bipolar junction transistor. The secondconductive loop can include a rectifier in series with two ends of theconductive loop. The rectifier can include a diode. The diode can be ap-n junction diode. The diode can be a Schottky diode. The Schottkydiode can be a silicon carbide diode. The diode is can be a Zener diode.The diode can be a gas diode. The second conductive loop can include adiscrete capacitor in series with two ends of the conductive loop. Thecapacitor can be connected in parallel with the diode.

The rotor circumferentially surrounds the stator.

The stator circumferentially surrounds the rotor.

The rotor and the stator are separated by an axial gap.

The electric machine is a motor.

Each of the rotor poles includes a material with a non-zero remanence.

A controller configured to apply a pulse of magnetizing current overtime to a stator coil of a stator pole when the stator pole is alignedwith a rotor pole across a nominal gap. The magnetizing current isconfigured to charge a magnetic field within the rotor pole throughinduced coupling. The controller is also configured to apply a loadcurrent pulsed over time to the stator coil when rotor pole ispositioned between adjacent stator poles. The load current pulsesstiffen the magnetic field within the rotor pole. The pulsed loadcurrent includes more pulses per increment of time than pulse themagnetizing current.

The rotor further includes permanently magnetic channels. The permanentmagnet channels can be located at respective rotor poles. The permanentmagnet channels can be located between the FPFCs and the stator. Thepermanent magnet channels can be located within a back-iron of therotor. The permanently magnetic channels can include ferrite. Thepermanently magnetic channels can include SmFeN. The permanentlymagnetic channels can include N35. The permanently magnetic channels caninclude N45.

The rotor includes a plurality of permanently magnetic spokes extendingfrom a central axis of the rotor. The spokes can be positioned betweenthe FPFCs.

The magnetizing current is applied as a single pulse of current overtime. The single pulse of current can include a half-sine wave. Thesingle pulse of current can include a half-square wave. The single pulseof current can include a half-trapezoidal wave. Applying the magnetizingcurrent can strongly couple the rotor pole to the stator pole.

The pulsed load current is applied as multiple current pulses over timeas a rotor rotates from a first pole to a second pole. The multiplecurrent pulses can include half-sine waves. The multiple current pulsescan include half-square waves. The multiple current pulses can includehalf-trapezoidal waves. The multiple current pulses can include fullsine waves. The multiple current pulses can include full square waves.The multiple current pulses can include full trapezoidal waves. Themultiple current pulses are not a function of a rotor speed. Themultiple current pulses are applied between five to ten hertz.

A rotor flux is maintained within a desired range during peak loadcondition. The desired range can vary within 50-100%. The desired rangecan vary within 65-100%. The desired range can vary within 80-100%.

The stator includes permanent magnet channels. The control methodfurther includes adjusting a strength of apparent magnetism within thepermanent magnet channels. The permanent magnet channels can includeferrite.

The rotor includes permanent magnet spokes. The control method furtherincludes adjusting a strength of apparent magnetism within the permanentmagnet spokes.

The variable magnetomotive force source includes a series of frequencyprogrammable flux channels (FPFCs). Each FPFC includes a conductive loopsurrounding an associated rotor pole. An excitement current of the FPFCis produced by the controlled magnetic field in the stator duringstart-up.

The electric rotor is rotated synchronously with the waveform.

Increasing the average flux includes applying a magnetizing current to astator coil of a stator pole when the stator pole is aligned with arotor pole across a nominal gap. The magnetizing current is configuredto stiffen a magnetic field within the rotor pole.

A pulsed load current is applied to the stator coil when rotor pole ispositioned between adjacent stator poles. The pulsed load current isconfigured to induce a motive force to the rotor. The pulsed loadcurrent includes more pulses than the magnetizing current.

A rotor pole of the electric machine magnetically softened. Magneticallysoftening can include changing an excitation waveform, produced bycurrent flowing through the stator, to allow magnetic decay within therotor pole, or adjusting a control circuit within the rotor pole.

The rotor pole magnetically hardened is in response to a sinusoidaldrive frequency.

The direct current is flowed for nine milliseconds and the inverteddirect current is pulsed for one millisecond.

A ratio of duration of direct current to a duration of pulsing invertedcurrent is 1:1 to 100:1. A ratio of duration of direct current to aduration of pulsing inverted current can be 5:1 to 15:1. A ratio ofduration of direct current to a duration of pulsing inverted current canbe 9:1.

A rotor is rotated responsive to flowing the direct current and pulsingthe inverted direct current. Then, an alternating current is flowedthrough a phase of the stator winding.

As used herein, the term “electric motor” also includes electricgenerators that generate electrical power from mechanical power.

By ‘nominal gap’ we mean a gap between relatively moving surfaces of thestator (or active magnetic component) and rotor (or passive magneticcomponent) poles, across which gap magnetic flux extends during motoroperation to induce a force on the rotor (or passive magneticcomponent). We use the term ‘active magnetic component’ to refer to thatportion of a motor that includes electrical windings associated withrespective magnetically permeable structures in which magnetic flux isgenerated by current flowing in the windings whose purpose generallyincludes directly transferring power into or out of the machine. Thepoles of an ‘active magnetic component’ are referred to as ‘activepoles’. The electrical windings will generally be held in fixed relationto corresponding active poles. A wound stator is an example of an activemagnetic component. We use the term ‘passive magnetic component’ torefer to that portion of the motor upon which a motive force is inducedby magnetic flux generated by the active magnetic component, to extendinto the passive magnetic component across the nominal gap. The poles ofa ‘passive magnetic component’ are referred to as ‘passive poles’. Anon-wound rotor is an example of a passive magnetic component. Thenominal gap may be radial, as in a radial gap motor, or axial, as in anaxial gap motor, for example, and may be filled with air or other gas,or even a liquid, such as a coolant.

By ‘flux barrier’ we mean a structure that defines at least oneelectrically conductive path in which a flow of current is induced by achanging magnetic field. Generally, eddy currents will be induced in theflux barrier that cause destructive interference of an impendingmagnetic field, such that the flux barrier effectively acts to inhibit achange in magnetic flux during motor operation, which in some cases willresult in a repulsive force that will act to increase an induced motiveforce on the passive poles. More specifically, a flux barrier allowszero flux to pass through it. Examples of flux barriers are described inapplication Ser. No. 16/534,217, filed on Aug. 7, 2019, which claimspriority to provisional application Ser. No. 62/715,386, filed on Aug.7, 2019, both of which are hereby incorporated by reference.

By ‘frequency programmable flux channel’ (FPFC) we mean a structure thatdefines at least one electrically conductive path around at least thepole segment of at least one rotor pole where the conductive path has asubstantially uniform inductance. In some implementations theelectrically conductive path fully encircles at least one rotor pole. Insome cases, a stator pole can be encircled as well. In some cases, theelectrically conductive loops can be non-overlapping. Generally, acurrent will be induced in the electrically conductive path to resist achange in the magnetic flux density of its corresponding pole. Thiscauses a reflective or resistant magnetic field, such that the FPFC cancontrollably attenuate a change in magnetic flux during operation, whichin some cases will result in a repulsive force that will act to increasean induced motive force on the passive poles. More specifically, incontrast with a flux barrier, an FPFC allows for zero flux or non-zeroflux to pass through it responsive to a control frequency received fromthe stator windings.

By ‘flux pinning’ we mean the resistance of topological movement of aflux location. In other words, flux is directed through a specifiedlocation, typically within a tooth of a rotor or a tooth of a stator.

By ‘electrical conductivity’ we mean the propensity of a material toconduct electricity. With respect to structures in which current isconstrained to flow in a principal direction, such as a wire, we meanthe conductivity in that principal direction.

By ‘electrically isolated from one another’ we mean that the ohmicresistance to an electric potential within a flux barrier is at least 10times less than the ohmic resistance between flux barriers. To say thatthey are isolated from one another external to the ferromagneticmaterial does not preclude that they are in electrical communicationthrough the ferromagnetic material of the layers. In fact, in many casesthe flux barriers are electrically connected through the ferromagneticmaterial.

By ‘electrically conductive’ we mean that a material or structure is atleast as conductive as amorphous carbon at typical motor operatingvoltages, or has a conductivity greater than 1000 Siemens per meter.Examples of electrically conductive materials include silver, copper,aluminum, nickel, iron, and electrical steel (grain oriented orotherwise).

Examples of non-conductive materials include non-filled resins, air,wood, and cotton. We use the term ‘insulator material’ to refer tomaterials that are non-conductive or not electrically conductive.

By ‘finite width’ we mean that the layer has opposite edges and doesnot, for example, extend around an entire circumference of the rotor (oralong an entire length of a linear passive magnetic component).

Similarly, by ‘finite thickness’ we mean that the layer extends to alimited depth and does not, for example, extend entirely through therotor.

By ‘electrical current skin depth’ we mean the depth from the surface ofa conductor at which electric current mainly flows, particularly eddycurrent induced from a magnetic field changing at a given frequency. Fora given material, skin depth can be calculated as:

δ≈1/√{square root over (πfμσ)}

where ‘f’ is the magnetic switching frequency, μ is the magneticpermeability (in H/mm) of the material, and σ is the electricalconductivity (in % AICS) of the material. By ‘magnetic permeability’ wegenerally mean the ability for a material to support the formation of amagnetic field. The magnetic permeability of a material can bedetermined in accordance with ASTM A772. When we say that a material is‘magnetically permeable’ we mean that it has a magnetic permeability ofat least 1.3×10⁻⁶ Henries per meter.

By ‘transmissible range’ we mean the frequency range over which themagnetic permeability depreciates by no more than 10 db relative to thepermeability at 60 hz, as measured under static frequency conditions(e.g., with permeability measurements for a given frequency taken overat least 5 cycles of the applied field).

Several features described within this disclosure include frequencyprogrammable flux channels (FPFCs) to increase the performance of anelectric motor, e.g., in high torque and power densities. The fluxbarriers have dynamic (or transient) diamagnetic properties. Byutilizing the FPFCs in the motor, significant gains in torque can beachieved by directing magnetic flux substantially more tangential, wherethe magnetic field is altered by redirecting a radial force (or normalforce) along the tangential direction. That is, the average force vectorduring operation is substantially more tangential where the predominantforce vector in traditional motor designs is radial in nature.

The magnetic permeability of the FPFCs can be controlled by adjusting amagnetic frequency of induced currents in the FPFCs, e.g., by pulsingcurrent through electrical windings of active poles. In such a way, theelectric motors can have significantly different magnetic properties atdifferent magnetic frequencies: at low frequencies, the properties ofthe FPFCs are ferromagnetic; at medium to high operational frequencies,the magnetic permeability of the flux barrier can be less than that ofair, and the properties of the FPFCs can be diamagnetic.

Some implementations describe herein can also create a high reactancecircuit where the magnetic field does not permeate through theelectromagnetic cycle, but is substantially reflected. This can reduceor eliminate flux fringing. Unlike a traditional permanent magnet (PM)motor, a reduced flux permeates FPFCs in the motors that utilize FPFCswithin their design, which can avoid demagnetization (coercive force)and excessive heat during operation. Moreover, the FPFCs can produce amagnetic field during operation depending on the frequency imparted bythe stator windings, so they can behave like PM motors in certainconditions, thus allowing lower energy permanent magnetic materials tobe used, or in some cases, eliminated entirely.

Aspects of this disclosure can be applied to various types of motors toimprove their performances. The motors can be radial-gap motors oraxial-gap motors or linear motors. The motors can be switched reluctancemotors (SRMs), induction motors (IMs), or permanent magnet motors (PMs),for example.

Various implementations disclosed herein can provide particularly highmotor performance with significant torque/force and power densities, andcan be used to provide essentially smooth and efficient output shaftpower for propelling vehicles, as well as in stationary systems. Thedesign concepts can more effectively increase torque and power byincreasing the saliency ratio of the motor itself, avoiding some of thetraditional trade-offs of harnessing one at the expense of the other.This motor may also obtain higher system efficiency during cycledoperation due to the avoidance of magnetic breaking that can occur withpermanent magnet motors under passive conditions.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of an example of an electric drivesystem.

FIG. 2A is a schematic illustration of a motor controller includingpower switching.

FIG. 2B is a schematic illustration of an example power switch for anelectrical winding.

FIG. 2C is a schematic illustration of a motor controller includingpower switching.

FIG. 3A is a schematic diagram of stator poles aligned with rotor poles,the rotor poles including an FPFC.

FIG. 3B is a diagram of a rotor pole becoming charged during alignment.

FIG. 3C is a schematic diagram of stator poles unaligned with rotorpoles, the rotor poles including an FPFC.

FIG. 3D is a diagram of a rotor hardening during misalignment.

FIGS. 4A-4C are views of an example passive frequency programmable fluxchannel (FPFC) that can be used with aspects of this disclosure.

FIG. 5A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 4A-4C.

FIG. 5B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 4A-4C.

FIG. 5C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 4A-4C.

FIG. 5D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 4A-4C.

FIGS. 6A-6C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 7A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 6A-6C.

FIG. 7B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 6A-6C.

FIG. 7C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 6A-6C.

FIG. 7D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 6A-6C.

FIGS. 8A-8C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 9A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 8A-8C mounted behind a permanentmagnet on the rotor.

FIG. 9B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 8A-8C mounted behind a permanentmagnet on the rotor.

FIG. 9C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 8A-8C mounted behind apermanent magnet on the rotor.

FIG. 9D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 8A-8C mountedbehind a permanent magnet on the rotor.

FIGS. 10A-10C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 11A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 10A-10C.

FIG. 11B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 10A-10C.

FIG. 11C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 10A-10C.

FIG. 11D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 10A-10C.

FIGS. 12A-12C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 13A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 12A-12C.

FIG. 13B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 12A-12C.

FIG. 13C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 12A-12C.

FIG. 13D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 12A-12C.

FIGS. 14A-14C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 15A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 14A-14C.

FIG. 15B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 14A-14C.

FIG. 15C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 14A-14C.

FIG. 15D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 14A-14C.

FIG. 16A is a perspective view of a rotor with the passive FPFCillustrated in FIGS. 14A-14C.

FIG. 16B is a planar cross-sectional view of the rotor illustrated inFIG. 16A. FIG.17A is a perspective view of an electric motor with anexample passive FPFC mounted behind a permanent magnet on a rotor. FIG.17B is a planar view of a portion of the electric motor illustrated inFIG. 17A.

FIG. 17C is a planar cross-sectional view of a portion of an electricmotor illustrated in FIG. 17A.

FIG. 17D is a perspective cross-sectional view of a portion of anelectric motor illustrated in FIG. 17A.

FIG. 18 is a perspective view of an example electric rotor with anexample passive FPFC.

FIGS. 19A-19C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 20A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 19A-19C.

FIG. 20B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 19A-19C.

FIG. 20C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 19A-19C.

FIGS. 21A-21C are views of an example passive FPFC that can be used withaspects of this disclosure.

FIG. 22A is a perspective view of a portion of an electric motor usingthe passive FPFC illustrated in FIGS. 21A-21C.

FIG. 22B is a planar view of a portion of an electric motor using thepassive FPFC illustrated in FIGS. 21A-21C.

FIG. 22C is a planar cross-sectional view of a portion of an electricmotor using the passive FPFC illustrated in FIGS. 21A-21C.

FIG. 22D is a perspective cross-sectional view of a portion of anelectric motor using the passive FPFC illustrated in FIGS. 21A-21C.

FIGS. 23A-23C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 24A is a perspective view of a portion of an electric motor usingthe rectified FPFC illustrated in FIGS. 23A-23C.

FIG. 24B is a planar view of a portion of an electric motor using therectified FPFC illustrated in FIGS. 23A-23C.

FIG. 24C is a planar cross-sectional view of a portion of an electricmotor using the rectified FPFC illustrated in FIGS. 23A-23C.

FIG. 24D is a perspective cross-sectional view of a portion of anelectric motor using the rectified FPFC illustrated in FIGS. 23A-23C.

FIGS. 25A-25C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 26A is a perspective view of a portion of an electric motor usingthe rectified FPFC illustrated in FIGS. 25A-25C.

FIG. 26B is a planar view of a portion of an electric motor using therectified FPFC illustrated in FIGS. 25A-25C.

FIG. 26C is a planar cross-sectional view of a portion of an electricmotor using the rectified FPFC illustrated in FIGS. 25A-25C.

FIG. 26D is a perspective cross-sectional view of a portion of anelectric motor using the rectified FPFC illustrated in FIGS. 25A-25C.

FIGS. 27A-27C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 28A is a perspective view of a portion of an electric motor usingthe rectified FPFC illustrated in FIGS. 27A-27C.

FIG. 28B is a planar view of a portion of an electric motor using therectified FPFC illustrated in FIGS. 27A-27C.

FIG. 28C is a planar cross-sectional view of a portion of an electricmotor using the rectified FPFC illustrated in FIGS. 27A-27C.

FIG. 28D is a perspective cross-sectional view of a portion of anelectric motor using the rectified FPFC illustrated in FIGS. 27A-27C.

FIGS. 29A-29C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 30A is a perspective view of a portion of an electric motor usingthe rectified FPFC illustrated in FIGS. 29A-29C.

FIG. 30B is a planar view of a portion of an electric motor using therectified FPFC illustrated in FIGS. 29A-29C.

FIG. 30C is a planar cross-sectional view of a portion of an electricmotor using the rectified FPFC illustrated in FIGS. 29A-29C.

FIG. 31A is a perspective view of an electric motor with an examplerectified FPFC mounted behind a permanent magnet on a rotor.

FIG. 31B is a planar view of a portion of the electric motor illustratedin FIG. 31A.

FIG. 31C is a planar cross-sectional view of a portion of an electricmotor illustrated in FIG. 31A.

FIGS. 32A-32C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 33A is a perspective view of a portion of an electric motor usingthe rectified FPFC illustrated in FIGS. 32A-32C.

FIG. 33B is a planar view of a portion of an electric motor using therectified FPFC illustrated in FIGS. 32A-32C.

FIG. 33C is a planar cross-sectional view of a portion of an electricmotor using the rectified FPFC illustrated in FIGS. 32A-32C.

FIG. 33D is a perspective cross-sectional view of a portion of anelectric motor using the rectified FPFC illustrated in FIGS. 32A-32C.

FIGS. 34A-34C are views of an example rectified FPFC that can be usedwith aspects of this disclosure.

FIG. 35A is a perspective view of a portion of an electric motor usingthe FPFC illustrated in FIGS. 34A-34C.

FIG. 35B is a planar view of a portion of an electric motor using theFPFC illustrated in FIGS. 34A-34C.

FIG. 35C is a planar cross-sectional view of a portion of an electricmotor using the FPFC illustrated in FIGS. 34A-34C.

FIG. 35D is a perspective cross-sectional view of a portion of anelectric motor using the FPFC illustrated in FIGS. 34A-34C.

FIG. 3 5E is a perspective view of an example motor using the FPFCillustrated in FIGS. 34A-34C.

FIG. 35F is a longitudinal cross-sectional view of the example motorillustrated in FIG.

FIG. 35G is a perspective cross-sectional view of the example motorillustrated in FIG. 35E.

FIG. 36A is a perspective view of an example axial-gap motor that can beused with aspects of this disclosure

FIG. 36B is a side view of the example axial gap motor illustrated inFIG. 36A.

FIG. 36C is a perspective view of the rotor used in the motorillustrated in FIG. 36A.

FIG. 36D is a perspective view of the stator used in the motorillustrated in FIG. 36A.

FIG. 37A is a perspective view of an example electric motor withdistributed windings that can be used with aspects of this disclosure.

FIG. 37B is a side view of the example electric motor illustrated inFIG. 37A.

FIG. 37C is a schematic view of the stator in the electric motorillustrated in FIG. 37A.

FIG. 37D is a planar cross-sectional view of the example motorillustrated in FIG. 37A.

FIG. 37E is a perspective cross-sectional view of the example motorillustrated in FIG. 37A.

FIGS. 38A-38B are perspective and planar views of an example motor withdistributed windings that can be used with aspects of this disclosure.

FIG. 39A is a perspective view of an example linear motor with rectifiedFPFCs on the “rotor”.

FIG. 39B is a longitudinal side view of the example linear motorillustrated in FIG. 39A.

FIG. 39C is a longitudinal cross-sectional view of the example linearmotor illustrated in FIG. 39A.

FIG. 39D is a perspective view of the stator of the example linear motorillustrated in FIG. 39A.

FIG. 39E is a perspective view of the “rotor” of the example linearmotor illustrated in FIG. 39A.

FIG. 40A is a perspective view of an example linear motor with rectifiedFPFCs on the “rotor” and the stator.

FIG. 40B is a longitudinal side view of the example linear motorillustrated in FIG. 40A.

FIG. 40C is a longitudinal cross-sectional view of the example linearmotor illustrated in FIG. 40A.

FIG. 40D is a perspective view of the stator of the example linear motorillustrated in FIG. 40A.

FIG. 41A is a hysteresis diagram of a “soft” magnetic material

FIG. 41B is a hysteresis diagram of a “hard” magnetic material

FIG. 42 is a schematic diagram of an electric motor with alignmentsbetween the rotor and the stator marked.

FIG. 43A is a graph showing torque of the rotor relative to the positionof the rotor relative to the stator.

FIG. 43B is a graph showing the current flow within an FPFC duringrotation of the rotor.

FIG. 44A is a set of graphs illustrating drive wave forms during alocked rotor condition.

FIG. 44B is a graph illustrating the transition from locked rotorcondition to moving rotor condition.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure describes an electric machine with a rotor and a stator.The stator defines multiple stator poles with associated electricalwindings. The rotor is movable with respect to the stator and includesmultiple rotor poles. The rotor poles include a magnetically permeablepole material. Together, the rotor and the stator define a nominal gapbetween the stator poles and the rotor poles. As will be described indetail throughout this disclosure, the rotor includes a series offrequency programmable flux channels (FPFCs). Each FPFC includes aconductive loop having some resistance surrounding an associated rotorpole. In some implementations, the stator and the rotor are arrangedsuch that the electrical windings in the stator excite a current withinat least one of the FPFCs during start-up. In some implementations, thestator and the rotor are arranged such that the electrical windings inthe stator magnetize at least one of the rotor poles during start-up. Inother words, the FPFCs can act as a variable magnetomotive force sourcecontrolled by the stator. This power transfer is generally synchronouswith the magnetic field produced by the stator. The intrinsic resistancewithin the conductive loop enables frequency modulated performancethrough resistive loads.

The FPFCs themselves work to reflect the magnetic field of the statoraway from the rotor. Such an arrangement can be used to protectpermanent magnets within the rotor from demagnetization forces inducedby the stator. As a result, weaker permanent magnetic components can beused within the rotor without reducing torque or power abilities of theelectric machine. In the context of this disclosure, “weaker magneticcomponents” means that relatively low-energy magnetic material can beused or a lesser amount of high energy material can be used than thosefound in conventional permanent magnetic motors of similar power andtorque ratings. Indeed, permanent magnetic materials can also beeliminated entirely with such an arrangement. Energy of a magneticmaterial, in the context of this disclosure, is a function of thecoercivity and the remanence of the material. In addition, geometry andamount of material can play a role in determining a total magneticenergy and flux density. For example, a small amount of a neodymiummagnet, such as NeFeB, can have a similar total energy product effect asa larger amount of magnetic ferrite.

In some implementations, an FPFC only includes a conductive loop withinherent resistance, capacitance, and inductance values. While theconductive loop may inherently include such values, additional passive,discrete components (e.g. resistors, capacitor, and inductors) can beadded to the conductive loop to achieve desired characteristics.Implementations which only use passive components are henceforthreferred to as “passive FPFCs”. In some implementations, the FPFC orconductive loop may define a capacitance, where, in someimplementations, the capacitance may be formed, inserted, and/or definedby a certain part of the FPFC or conductive loop. In otherimplementations, the FPFC or conductive loop may have a resonantfrequency. In some implementations, the resonant frequency of the FPFCmay be in the transmissible range of the magnetically permeable pole orFPFC material.

The magnetomotive force produced by the passive FPFCs can create areduced torque moment in operation during recharge (fieldstrengthening). In other words, the magnetic force induced within therotor might require a recharge at certain intervals in operation whenthe field of the FPFC weakens. Field weakening of the FPFCs can occur intwo ways. In the first, the field may weaken over time due to theinherent reactance within the FPFC. In the second, a permanentmagnetomotive force source (e.g., a permanent magnet) may weaken whenloaded. Recharge cycles to counteract these effects can reduceefficiency and create torque ripple. To mitigate this issue, the FPFCcan include a rectifier (henceforth referred to as a “rectified FPFC”)to essentially “shut-down” the circuit during the recharge cycle,preventing current from crossing flux in the associated rotor pole (andhence a resultant reduced torque moment). Such an arrangement onlyallows current to pass through the loop in one direction and allows therectified FPFC to maintain the desired flux during operation.

While maintaining a desired flux within the rotor can be advantageous,it is conceivable for operation modes where it may be desired to weakenthe flux more rapidly than inherent field weakening allows, for example,high-speed low-load conditions. Such operation modes can include therotor coasting or fly-wheeling when the electric machine is not workingas a generator. Such operating conditions can be done with a rectifiedFPFC, but further control and sensitivity in reducing the magnetic dragon the system during such operations can be provided by a logic circuitwithin the FPFC. The logic circuit can include active components such asa field effect transistor, a dual gate field effect transistor, or abipolar junction transistor.

Such circuitry can be controlled directly with a brushed connection, bylight sensitive diodes, or by other wireless communication mediums. Suchan arrangement is henceforth referred to as an “active FPFC”.

Implementations of the present disclosure provide systems, devices, andmethods of using FPFCs to increase performance of electric motors.Various designs/configurations of FPFCs for the motors are presented anddiscussed. The FPFCs are configured to exhibit varying diamagneticeffects based on the current operating mode, such that variablemagnetomotive force sources within the rotor can be actively controlledand adjusted primarily by the magnetic field produced by the statorwindings.

Example Electric Drive System

FIG. 1 illustrates an electric drive system 100 that includes anelectric motor 102 and a motor controller 107 coupled to the electricmotor 102. The motor controller 107 is configured to operate theelectric motor 102 to drive a load 104. The load 104 can be anadditional gear train such as a planetary gear set or another motorwhere multiple motors can be linked and operated in parallel.

The electric motor 102 has an output shaft 107 rotatable with respect toa motor housing 105, which is considered to be a datum with respect torotations and other motions of motor components. In use, the outputshaft 107 can be coupled to the load 104 to which the motor 102 canimpart rotary power when electrically activated by appropriateelectrical power and signals from the motor controller 107. The outputshaft 107 may extend through the motor and be exposed at both ends,meaning that rotary power can be transmitted at both ends of the motor.Housing 105 can be rotationally symmetric about the rotation axis ofoutput shaft, but may be of any external shape and can generally includemeans for securing the housing to other structure to prevent housingrotation during motor operation.

The electric motor 102 includes an active magnetic component 106 such asa stator and a passive magnetic component 108 such as a rotor. Forillustration purposes, in the following, stator is used as arepresentative example of the active magnetic component and rotor isused as a representative example of the passive magnetic component.

The rotor 106 is associated with the stator 108 and can be disposedwithin the stator 108, e.g., in an internal rotor radial-gap motor, orparallel to the stator, e.g., in an axial-gap motor, or in a linearmotor. As described more fully below, electrical activity in the stator108, properly controlled, drives motion of the rotor 106. The rotor 106is rotationally coupled to the output shaft 107, such that anyrotational component of resultant rotor motion is transmitted to theoutput shaft 107, causing the output shaft 107 to rotate. The stator 108is fixed to the motor 102 such that during operation the rotor 106 movesabout the stator 108 or parallel to the stator 108.

The stator 108 defines multiple stator poles with associated electricalwindings and the rotor 106 includes multiple rotor poles, such as theexample illustrated with further details in FIGS. 5A-5D. The rotor 106defines, together with the stator 108, a nominal air gap between thestator poles and the rotor poles, such as the example as illustratedwith further details in FIGS. 5A-5D later within this disclosure. Therotor 106 is movable with respect to the stator 108 along a motiondirection. As illustrated in FIG. 2A, the stator 108 has multipleindependently activatable windings 132 spaced apart circumferentiallyabout the rotor 106. The multiple adjacent windings 132 of the stator108 are activatable simultaneously as a winding set, and the stator 108can include multiple such multi-winding sets spaced about the stator108. The motor 102 may also include a winding controller 130 with a setof switches 134 operable to activate the windings 132 of the stator 108.The switches 134 can be semiconductor switches, e.g., transistors suchas metal-oxide-semiconductor field-effect transistors (MOSFETs). Thewinding controller 130 is coupled to gates of the switches 134 andoperable to send a respective control voltage to each switch 134. Thecontrol voltage can be a direct current (DC) voltage. The windingcontroller 130 can be in the motor controller 107.

While only three switches are shown in FIG. 2A, it will be understoodthat the motor controller 107 can have a switch for each stator pole, ormultiple switches to energize multiple coils. Adjacent pole pairs may bewired in series via a common switch, but in such cases theinstantaneously faster of the two moving rotors can generate a slightlylarger counter-electromotive force (EMF) or back-EMF and instantaneouslydraw more relative electrical power as compared to the slower pole,thereby providing additional acceleration and separation of relativevelocities. Higher frequency excitation can decrease effects of lowfrequency harmonic ripple during operation. The switches 134 can bewired in parallel to balance relative speed between multiple rotors in anested configuration by using parallel inductive load reactors. Incertain implementations with nested rotor configurations, individualrotors in the system can be driven individually and any harmonicfrequency may be bypassed from one rotor to another by decreasing theloading on a given rotor. In other implementations, rotors can be nestedas pairs to balance the force between an inner and outer ring locally.FIG. 2B shows another example power switch 200 for an individualelectrical winding 132. The power switch 200 can have an H-bridgecircuit including four switching elements 202 a, 202 b, 202 c, 202 d,with the electrical winding 132 at the center, in an H-likeconfiguration. The switching elements 202 a, 202 b, 202 c, 202 d can bebi-polar or FET transistors. Each switching element 202 a, 202 b, 202 c,202 d can be coupled with a respective diode D1, D2, D3, D4. The diodesare called catch diodes and can be of a Schottky type. The top-end ofthe bridge is connected to a power supply, e.g., a battery V_(bat), andthe bottom-end is grounded. Gates of the switching elements can becoupled to the winding controller 130 which is operable to send arespective control voltage signal to each switching element. The controlvoltage signal can be a DC voltage signal or an AC (alternating current)voltage signal. The switching elements can be individually controlled bythe controller 130 and can be turned on and off independently. In somecases, if the switching elements 202 a and 202 d are turned on, the leftlead of the stator is connected to the power supply, while the rightlead is connected to ground. Current starts flowing through the stator,energizing the electrical winding 132 in a forward direction. In somecases, if the switching elements 202 b and 202 c are turned on, theright lead of the stator is connected to the power supply, while theleft lead is connected to ground. Current starts flowing through thestator, energizing the electrical winding 132 in a reverse, backwarddirection. That is, by controlling the switching elements, theelectrical winding 132 can get energized/activated in either of twodirections.

FIG. 2C is a schematic illustration of a motor controller includingpower switching. FIG. 2C is substantially similar to FIG. 2A with theexception of any differences described herein. As illustrated in FIG.2C, each rotor winding 132 phase (A, B, C) has a switch between apositive power rail 148 and the individual winding 132 and a switchbetween each rotor winding phase and a negative power rail 149. Voltageis supplied to both the positive rail 148 (positive voltage) and thenegative rail (negative voltage) is supplied in a substantially constantmanner while the controller 130 controls switches 150 to exchangecurrent between the windings 132 and the individual power rails (148,149). In other implementations, such a controller and power switches maybe connected and configured to operate from a current source.

The motor controller 107, e.g., the winding controller 130, can beconfigured to sequentially operate the switches 134, 150, or 200 forrespective pole energization duty cycles to generate magnetic fluxacross the air gap between the stator poles and rotor poles, asdescribed with further details throughout this disclosure. The switchescan be controlled to sequentially energize stator poles to create alocal attraction force pulling on the rotor. Such a sequentialenergization (or activation) can cause a rotation of the rotor 106, theoutput shaft 107, and the load 104.

As discussed in further detail below, various types and configurationsof FPFCs can be implemented in the rotor 106 and/or the stator 108. TheFPFCs can adjustably attenuate flux passing through them.

In some examples, a FPFC is made of a single material, such as aluminum,copper, brass, silver, zinc, gold, pyrolytic graphite, bismuth,graphene, or carbon-nanotubes. In some examples, ferromagneticcombinations of materials, such as copper-iron, nickel-iron, lead-iron,brass-iron, silver-iron, zinc-iron, gold-iron, bismuth-iron,aluminum-iron, pyrolytic graphite-iron, graphene-iron,carbon-nanotubes-iron, or Alinco (aluminum-nickel-cobalt) alloys can beused as a flux barrier, in many cases with an electric conductivityhigher than ferromagnetic material (e.g., iron) making up the rotorpoles. In some cases, the FPFC, e.g., made of copper-iron, has aneffective magnetic permeability lower than the ferromagnetic material.In some cases, the FPFC, e.g., made of nickel-iron, has an effectivemagnetic permeability higher than the ferromagnetic material. Ingeneral, the FPFC is constructed as a shielded pole of an electricallyconductive material forming a loop about a core of a core material moremagnetically permeable than the electrically conductive material. Due tothe electrically conductive material of the loop, the shielded pole canalso have an effective electric conductivity higher than the corematerial (e.g., iron). The FPFCs may include multiple materials arrangedas alternating layers. In some implementations, the alternating layersfrom interlayer interfaces of different materials. In someimplementations, the first layer may be more electrically conductivethan the second layer. In some implementations, the second layer of thepair is more magnetically permeable than the first layer. In someimplementations, the first and second layers each have an electricalcurrent skin depth greater than a respective layer thickness in adirection perpendicular to the nominal gap at a particular operatingfrequency.

Another material property of interest, which we refer to as the EMFShielding Factor, is the quotient of electrical conductivity andmagnetic permeability (e.g., Siemens per Henry). The EMF ShieldingFactors of two materials may be determined simultaneously by placingequally sized samples of the materials on a non-conductive support andmoving them between two parallel Helmholtz coils with a diameter greaterthan the samples, such that their primary plane of conduction (e.g., theorientation of the plane as is experienced during operation in amagnetic system) is perpendicular to the magnetic fields produced duringexcitation of the Helmholtz coils. For a given excitation waveform(e.g., voltage, shape, and frequency) the current of the Helmholtz coilswill be proportional to the EMF Shielding Factor of the material betweenthe coils, such that an increase in the EMF Shielding Factor will beobserved as an increase in the current during constant excitation.

As noted above and discussed in further detail below, the FPFC can beconfigured to be diamagnetic. The magnetic permeability of the fluxbarrier can be controlled by adjusting an induced frequency through theFPFC. In such a way, the motor can have significantly different magneticproperties at different magnetic frequencies.

To operate the FPFC under operational frequencies, sinusoidal or squarewave control can be used where the stator poles interact with the FPFCsas the primary power source of the machine. In operation, a pulsed tocontinuous sine wave may be used, which occurs as a function of therotor speed where pulsing occurs from to locked conditions (e.g., 0hertz). This is because at higher speeds, the pulse and charge cyclesoverlap as the mechanical timing reaches the pulse frequency. Therefore,the waveform adopts a fundamental wave. The transition to synchronousoperation can occur in certain implementations at 10,000 hertz, morepreferably from 1,000 hertz-10,000 hertz, more preferably 100 hertz-500hertz, more preferably 10 hertz-100 hertz. For some implementations,10,000 hertz can be considered substantially synchronous operation, morepreferably 10,000 hertz, more preferably 1,000 hertz, more preferably100 hertz, more preferably 10 hertz. Under such generally synchronousconditions further frequency modulation can occur. For example, asillustrated in FIGS. 3A-3D, during an energization duty cycle of eachactive pole the motor controller 107 is configured to pulse a current302 through the winding of the stator pole 304. Unlike induction motorsthat pulse each pole once in succession at low speeds, motor controller107 pulses an inverted current 306 multiple times when a stator pole 304is between two adjacent rotor poles 308. This magnetically “stiffens”the FPFC 310. More details on the charging and stiffening cycles aredescribed throughout this disclosure. Such multiple inverted pulses 306to the same pole, before pulsing a subsequent pole, make up oneenergization duty cycle. In some examples, the motor controller pulsescurrent through the winding of an active stator pole 304 during anenergization duty cycle of the pole, including a sequence of at leastthree inverted pulses 306. The electrical circuit including theelectrical windings of each pole is configured such that a ratio ofinverted pulses 306 to pulses 302 through the stator windings is atleast 4:1, in some cases at least 7:1, or in some cases even at least10:1. In some operating conditions, inverted pulses 306 are notnecessary, and the motor can be driven with a standard sinusoidal ortrapezoidal wave-form through the stator pole 304.

The combination of pulsed current 302 and inverted pulsed current 306causes alternating magnetic intensities, e.g., magnetic fields, whichinduce currents in the FPFC 310. The induced current generates asecondary magnetic field opposing the applied alternating magneticfield, thereby producing a repelling force. The repelling force canconcentrate and redirect the magnetic flux substantially moretangentially along a direction of relative motion between the rotor andthe stator, to therefore increase the force available to do work. Also,FPFCs 310 having different materials or designs can have differentproperties. Thus, the generated horizontal force is with a function ofthe magnetic frequency and the structure of the FPFC 310.

The magnetic frequency for the FPFC 310 (and the generated force) can bedetermined by the pulse frequency of the current through the winding ofthe stator pole 304 during the energization duty cycle for each activepole 304. The pulse frequency can be, for example, in some cases between2 hertz and 1 Mhertz, in some cases between 10 hertz and 20 khertz, andin some cases between 100 hertz and 5,000 hertz and in some casesbetween 5,000 and 15,000 hertz, and in some cases between 15,000 hertzand 25,000 hertz and above depending on the fundamental. In some cases,the motor controller is configured to maintain pulse frequency duringmotor speed changes, up to at least a motor speed at which anenergization duty cycle frequency for each active pole is at leastone-half the pulse frequency. In some cases, the motor controller isconfigured to pulse current only below a motor speed corresponding toone pulse per energization duty cycle. In some implementations, at leastone of the electrical windings includes multiple coils conductivelyconnected in parallel and wound about a common core. Such electricalwinding can have a low reactance, enabling faster decay of currentbetween pulses.

Example Motors

In the following, various designs/configurations of frequencyprogrammable flux channels (FPFCs) for electric motors, radial-gapmotors, axial-gap motors, and linear motors are presented and discussed.While variations of these motors are illustrated and described indetail, other motor designs with FPFCs can be constructed withoutdeparting from this disclosure.

Radial-Gap Motors with Passive FPFCs

This section primarily describes implementations relating to radial-gapmotors using passive FPFCs. In the context of this disclosure, a“passive” FPFC is an FPFC that that includes nothing more than a shortedconductor fully encircling at least one pole on a rotor. That is, onlythe inherent capacitance, inductance, and resistance defined by the FPFCis present without the addition of other discrete components. In thevarious implementations described herein, both internal rotors andexternal rotors are described. While individual implementations may beillustrated as either using an internal or an external rotor, it isnoted that aspects of the implementations described herein areapplicable to both internal rotors and external rotors regardless if theindividual implementation described.

FIGS. 4A-4C are views of an example passive frequency programmable fluxchannel 400 (FPFC) that can be used with aspects of this disclosure.FIG. 5A is a perspective view of a portion of an electric motor 500using the passive FPFC 400 illustrated in FIGS. 4A-4C. FIG. 5B is aplanar view of a portion of the electric motor 500 using the passiveFPFC 400 illustrated in FIGS. 4A-4C. FIG. 5C is a planar cross-sectionalview of a portion of the electric motor 500 using the passive FPFC 400illustrated in FIGS. 4A-4C. FIG. 5D is a perspective cross-sectionalview of a portion of the electric motor 500 using the passive FPFC 400illustrated in FIGS. 4A-4C. FIGS. 4A-5D are used in combination todescribe the electric motor 500 and FPFC 400.

The electric machine 500 includes a stator 502 defining multiple statorpoles 504 with associated electrical windings 506. A rotor 508 includesmultiple rotor poles 510. The rotor 508 is movable with respect to thestator 502. In this case, the rotor 508 is arranged to rotate within thestator 502. The rotor 508 and the stator 502 together define a nominalgap 512 between the stator poles 504 and the rotor poles 510. In thiscase, the nominal gap 512 is a radial gap with the stator 502circumferentially surrounding the rotor 508. The rotor poles 510 includea magnetically permeable pole material, such as iron. The rotor 508 alsoincludes a series of frequency programmable flux channels (FPFCs) 400.Each FPFC 400 includes a conductive loop 402 that surrounds or encirclesan associated rotor pole 510. In the illustrated implementation, eachrotor pole 510 is encircled. The stator 502 and the rotor 508 arearranged such that the electrical windings 506 in the stator 502 canexcite a current within the FPFCs 400 during start-up. In other words,the rotor 508 includes a variable magnetomotive force source, the FPFCs400, controllable by a controlled magnetic field produced by statorwindings 506. Cleats or brushes providing current to the rotor 508through conduction during start-up are unnecessary in all of theimplementations described herein.

The rotor can be made of a magnetically permeable material, such asiron. In some implementations, the rotor 508 can be made-up of rotorlaminations 514 to reduce eddy currents within the back-iron of therotor 508. Similarly, the stator 502 can be made-up of statorlaminations 516 to reduce eddy currents within the back iron of thestator 502. In some implementations, the poles 510 of the rotor 508include a material with a non-zero remanence. In the illustratedimplementation, the rotor poles include a lip 518 arranged to retaineach FPFC 400 on their respective rotor pole 510 at the desiredoperating speed. Other arrangements can be used to retain each FPFC 400,such as various fasteners, adhesives, or resins.

As illustrated, the rotor 508 includes several permanently magneticspokes 520 extending from a central axis of the rotor 508. Each of thepermanently magnetic spokes 520 is positioned between the poles 510,including the FPFCs 400, of the rotor. The permanently magnetic spokes520 can penetrate the entire longitudinal length of the rotor 508 orpartially though the rotor 508. In some implementations, the permanentlymagnetic spokes 520 can be made-up of multiple layers or laminations.The permanently magnetic spokes 520 can be made from a variety ofmaterial, including ferrite, SmFeN, N35, and N45. While lower powerpermanent magnetic material is typically used, higher powered magneticmaterial in lower quantities can be used without departing from thisdisclosure. While illustrated and described as having a spoke-like shapeand being positioned between the rotor poles 510 and behind the FPFCs400, other arrangements are possible without departing from thisdisclosure. In some implementations, no permanent magnetic material isused.

Regarding the FPFCs 400, they include at least one conductive loop 402that has at least one turn of shorted conductive material. That is, theconductive material fully encircles a rotor pole 510 and shorts itselfto form a loop. In some implementations, the conductive loop 402includes material more conductive than a rotor core material. In someimplementations, the conductive loop 402 includes material lessmagnetically permeable than a rotor core material. Materials that meetone or both of these criteria include but are not limited to singlematerial, such as aluminum, copper, brass, silver, zinc, gold, pyrolyticgraphite, bismuth, graphene, or carbon-nanotubes. In some examples,ferromagnetic combinations of materials, such as copper-iron,nickel-iron, lead-iron, brass-iron, silver-iron, zinc-iron, gold-iron,bismuth-iron, aluminum-iron, pyrolytic graphite-iron, graphene-iron, orcopper-carbon-nanotubes, carbon-nanotubes-iron, or Alinco(aluminum-nickel-cobalt) alloys can be used as a flux barrier, in manycases with an electric conductivity higher than ferromagnetic material(e.g., iron) making up the rotor poles. In some cases, the FPFC, e.g.,made of copper-iron, has an effective magnetic permeability lower thanthe ferromagnetic material. In some cases, the FPFC, e.g., made ofnickel-iron, has an effective magnetic permeability higher than theferromagnetic material. In general, the FPFCs 400 have a substantiallyuniform inductance, particularly in a radial direction. Such a criteriaallows for full skin effect penetration of each FPFC 400 at a specifieddrive frequency. Conductor geometry, such as thickness of individualconductors within the conductive loop, is considered when designing theFPFCs 400. In some implementations, drive frequencies can extend between0 hertz and 20 hertz. In some implementations, drive frequencies canrange between 100 hertz and 2000 hertz. In other implementations, drivefrequencies can operation in excess of 20 kilohertz. While the FPFCs 400are illustrated as having a substantially rectangular cross-section inthis implementation, other cross-sectional shapes can be used withoutdeparting from this disclosure. Other examples of FPFCs using differentcross-sectional shapes are described throughout this disclosure aredescribed throughout this disclosure.

FIGS. 6A-6C are views of an example passive FPFC 600 that can be usedwith aspects of this disclosure. FIG. 7A is a perspective view of aportion of an electric motor 700 using the passive FPFC 600 illustratedin FIGS. 6A-6C. FIG. 7B is a planar view of a portion of the electricmotor 700 using the passive FPFC 600 illustrated in FIGS. 6A-6C. FIG. 7Cis a planar cross-sectional view of a portion of the electric motor 700using the passive FPFC 600 illustrated in FIGS. 6A-6C. FIG. 7D is aperspective cross-sectional view of a portion of the electric motor 700using the passive FPFC 600 illustrated in FIGS. 6A-6C. The electricmotor 700 is substantially similar to the electric motor 500 with theexception of any differences described herein.

The FPFCs 600 have a substantially circular cross-section with a smallercross-sectional area than the FPFCs 400. The smaller cross-sectionalarea can allow for full skin depth penetration at higher operatingfrequencies. The rotor poles 710 within the rotor 708 are shortened tohelp retain the geometry of their respective FPFCs 600.

FIGS. 8A-8C are views of an example passive FPFC 800 that can be usedwith aspects of this disclosure. FIG. 9A is a perspective view of aportion of an electric motor 900 using the passive FPFC 800 illustratedin FIGS. 8A-8C. FIG. 9B is a planar view of a portion of the electricmotor 900 using the passive FPFC 800 illustrated in FIGS. 8A-8C mountedbehind a permanent magnet 920 on the rotor 908. FIG. 9C is a planarcross-sectional view of a portion of the electric motor 900 using thepassive FPFC 800 illustrated in FIGS. 8A-8C mounted behind a permanentmagnet 920 on the rotor 908. FIG. 9D is a perspective cross-sectionalview of a portion of the electric motor 900 using the passive FPFC 800illustrated in FIGS. 8A-8C mounted behind a permanent magnet 920 on therotor 908. The electric motor 900 is operates on similar principles tothe electric motor 500, and should be considered to be similar to theelectric motor 700 with the exception of any differences describedherein.

The electric motor 900 has a rotor 908 circumferentially surrounding astator 902. The FPFCs 800 surround their respective rotor poles 910 andhave a rounded rectangular cross section. In the illustratedimplementation, the rotor poles include a lip 918 arranged to retaineach FPFC 800 on their respective rotor pole 910. Other arrangements canbe used to retain each FPFC 800, such as various fasteners, adhesives,or resins. As the illustrated implementation includes an external rotor908, centrifugal force during operation can also help retain the FPFCs800.

In this implementation, the FPFCs are positioned behind permanentmagnets 920 that are located each of the rotor poles 910. The permanentmagnets 920 can be made from a variety of material, including ferrite,SmFeN, N35, N45. While lower power permanent magnetic material istypically used, higher powered magnetic material in lower quantities canbe used without departing from this disclosure. The permanent magnets920 can extend across the entire longitudinal length of each rotor pole910 or partially across each rotor pole 910. In some implementations,the permanent magnets 920 can be made-up of multiple layers orlaminations.

FIGS. 10A-10C are views of an example passive FPFC 1000 that can be usedwith aspects of this disclosure. FIG. 11A is a perspective view of aportion of an electric motor 1100 using the passive FPFC 1000illustrated in FIGS. 10A-10C. FIG. 11B is a planar view of a portion ofthe electric motor 1100 using the passive FPFC 1100 illustrated in FIGS.10A-10C. FIG. 11C is a planar cross-sectional view of a portion of anelectric motor 1100 using the passive FPFC 1000 illustrated in FIGS.10A-10C. FIG. 11D is a perspective cross-sectional view of a portion ofthe electric motor 1100 using the passive FPFC 1000 illustrated in FIGS.10A-10C. The electric motor 1100 is substantially similar to theelectric motor 900 with the exception of any differences describedherein.

The FPFC 1000 includes multiple, thin laminations 1002 that encircleeach rotor pole. The thinner laminations can allow for full skin depthpenetration at higher operating frequencies. Each lamination 1002 iselectrically isolated from one-another within each FPFC 1000. In thisimplementation, no permanent magnets are used. This is because the FPFCs1000 are capable of reflecting the entirety of the flux produced by thestator windings 1106, resulting in an electromotive force acting on therotor 1108. This capability is inherent in all of the FPFCimplementations described herein. In the illustrated implementation, therotor poles 1110 do not include a lip to retain the FPFCs 1000 in placearound their respective rotor poles 1110. Instead, fasteners, adhesive,resin, a friction fit, or an interference fit can be used to retain theFPFCs 1000 around their respective rotor poles 1100.

FIGS. 12A-12C are views of an example passive FPFC 1200 that can be usedwith aspects of this disclosure. FIG. 13A is a perspective view of aportion of an electric motor 1300 using the passive FPFC 1200illustrated in FIGS. 12A-12C. FIG. 13B is a planar view of a portion ofthe electric motor 1300 using the passive FPFC 1300 illustrated in FIGS.12A-12C. FIG. 13C is a planar cross-sectional view of a portion of theelectric motor 1300 using the passive FPFC 1200 illustrated in FIGS.12A-12C. FIG. 13D is a perspective cross-sectional view of a portion ofthe electric motor 1300 using the passive FPFC 1200 illustrated in FIGS.12A-12C. The electric motor 1300 is substantially similar to theelectric motor 500 with the exception of any differences describedherein.

The FPFCs 1200 include shorted windings of at least one loop similar tothe windings 1306 used within the stator 1302. In other words, a singleconductor 1202 encircles a respective rotor pole 1310 multiple timesbefore shorting on itself. Such an arrangement allows for conductor 1202within the FPFC 1200 to include a smaller cross-sectional area can allowfor full skin depth penetration at higher operating frequencies. Such anarrangement also allows for improved uniform inductance across the FPFC1200 when compared to solid conductors with a larger cross sectionalarea per loop around each pole 1310.

FIGS. 14A-14C are views of an example passive FPFC 1400 that can be usedwith aspects of this disclosure. FIG. 15A is a perspective view of aportion of an electric motor 1500 using the passive FPFC 1400illustrated in FIGS. 14A-14C. FIG. 15B is a planar view of a portion ofthe electric motor 1500 using the passive FPFC 1400 illustrated in FIGS.14A-14C. FIG. 15C is a planar cross-sectional view of a portion of theelectric motor 1500 using the passive FPFC 1400 illustrated in FIGS.14A-14C. FIG. 15D is a perspective cross-sectional view of a portion ofthe electric motor 1500 using the passive FPFC 1400 illustrated in FIGS.14A-14C. The electric motor 1500 is substantially similar to theelectric motor 900 with the exception of any differences describedherein.

The FPFCs 1400 each include a shorted coil 1402. In other words, asingle conductor encircles a respective rotor pole 1510 multiple timesbefore shorting on itself. Such an arrangement allows for the conductorwithin the FPFC 1400 to include a smaller cross-sectional area can allowfor full skin depth penetration at higher operating frequencies. Such anarrangement also allows for improved uniform inductance across the FPFC1400 when compared to solid conductors with a larger cross-sectionalarea. While the illustrated implementation includes a conductor with asubstantially rectangular cross-section, other cross-section shapes canbe used without departing from this disclosure.

The rotor 1508 can include multiple permanently magnetic channels 1520.In some implementations, multiple permanently magnetic channels 1520 canbe included within each rotor pole 1510. As illustrated each poleincludes four channels 1520 arranged in a substantial “M” of “W”configurations; however, other arrangements can be used withoutdeparting from this disclosure. The permanently magnetic channels 1520can be include a variety of material, including ferrite, SmFeN, N35,N45. While lower power permanent magnetic material is typically used,higher powered magnetic material in lower quantities can be used withoutdeparting from this disclosure. The permanently magnetic channels 1520can extend across the entire longitudinal length of each rotor pole 1510or partially across each rotor pole 1510. In some implementations, thepermanently magnetic channels 1520 can be made-up of multiple layers orlaminations.

FIG. 16A is a perspective view of a rotor 1608 with the passive FPFC1400 illustrated in FIGS. 14A-14C. FIG. 16B is a planar cross-sectionalview of the rotor 1608 illustrated in FIG. 16A. The electric rotor 1608illustrated in FIGS. 16A-16B is substantially similar to the rotorillustrated in FIGS. 15A-15D with the exception of any differencesdescribed herein. In this implementation, each pole includes a single“V”-shaped permanently magnetic channel 1620. Other arrangements can beused without departing from this disclosure.

FIG. 17A is a perspective view of an electric motor 1700 with an examplepassive FPFC 1701 mounted behind a permanent magnet 1720 on a rotor1708. FIG. 17B is a planar view of a portion of the electric motor 1700illustrated in FIG. 17A. FIG. 17C is a planar cross-sectional view of aportion of the electric motor 1700 illustrated in FIG. 17A. FIG. 17D isa perspective cross-sectional view of a portion of the electric motor1700 illustrated in FIG. 17A. The electric motor 1700 is substantiallysimilar to the electric motor 900 illustrated in FIGS. 9A-9D with theexception of any differences described herein. The FPFCs 1701 used inthe electric motor 1700 are similar to the FPFCs 1200 illustrated inFIGS. 12A-12C. That is, the FPFCs 1701 are made-up of windings. Aconductor within the winding encircles a respective rotor pole 1710multiple times before shorting upon itself.

FIG. 18 is a perspective view of an example electric rotor 1800 with anexample passive FPFC 1801. The FPFC 1801 is made of litz wire. Asillustrated, a shorted ribbon of litz wire encircles each rotor pole1810 and is shorted at a termination point 1803, forming a conductiveloop. Litz wire includes multiple thin wire strands that do not occupythe same radial positon within the FPFC over the length of theconductive loop. That is, there is a weaving or twisting pattern to thewires such that individual strands on the inside of the FPFC for aportion of the length of the FPFC and are on the outside of the FPFC fora portion of the length of the FPFC. In some implementations, thethickness of the individual strands is less than that of the effectiveskin depth. That is, the thickness of the strands is small enough forfull skin effect penetration for a desired drive frequency. Such anarrangement helps ensure that the conductive loop formed by each FPFC1801 has a substantially uniform inductance, particularly in the radialdirection.

FIGS. 19A-19C are views of an example passive FPFC 1900 that can be usedwith aspects of this disclosure. FIG. 20A is a perspective view of aportion of an electric motor 2000 using the passive FPFC 1900illustrated in FIGS. 19A-19C. FIG. 20B is a planar view of a portion ofthe electric motor 2000 using the passive FPFC 1900 illustrated in FIGS.19A-19C. FIG. 20C is a planar cross-sectional view of a portion of theelectric motor 2000 using the passive FPFC 1900 illustrated in FIGS.19A-19C. The electric machine 2000 is substantially similar to theelectric machine 1100 illustrated in FIGS. 11A-11D with the exception ofany differences described herein.

In the illustrated implementation, the FPFC 1900 includes an innerconductive loop 1902 shorted to an outer conductive loop 1904. The innerconductive loop encircles a first rotor pole 2010 a while the outerconductive loop encircles two adjacent poles 2010 b. FPFCs may be nestedto create local inductive asymmetries between adjacent rotor teeth. Suchan implementation can create local inductive asymmetries betweenadjacent rotor teeth and helps enable torque generation at zero rpmunder locked rotor conditions.

FIGS. 21A-21C are views of an example passive FPFC 2100 that can be usedwith aspects of this disclosure. FIG. 22A is a perspective view of aportion of an electric motor 2200 using the passive FPFC 2100illustrated in FIGS. 21A-21C. FIG. 22B is a planar view of a portion ofthe electric motor 2200 using the passive FPFC 2100 illustrated in FIGS.21A-21C. FIG. 22C is a planar cross-sectional view of a portion of theelectric motor 2200 using the passive FPFC 2100 illustrated in FIGS.21A-21C. FIG. 22D is a perspective cross-sectional view of a portion ofthe electric motor 2200 using the passive FPFC 2100 illustrated in FIGS.21A-21C. The electric motor 2200 is substantially similar to theelectric motor 2100 illustrated in FIGS. 20A-20C with the exception ofany differences described herein.

In the illustrated implementation, the FPFC 2100 includes an innerconductive loop 2102 and an outer conductive loop 2104 that areelectrically isolated from one another. The inner conductive loop 2102encircles a first rotor pole 2210 a, while the outer conductive loop2104 encircles two adjacent poles 2210 b. Both the inner loop 2102 andthe outer loop 214 include coiled conductors that encircle theirrespective pole(s) (2210 a and 2210 b) before shorting upon themselves.

In some implementations, the inner conductive loop 2102, the outerconductive loop 2104, or both, include material more conductive than arotor core material. In some implementations, the first conductive loop2102, the second conductive loop 2104, or both, include material lessmagnetically permeable than a rotor core material. Materials that fitthese criteria include but are not limited to a single material, such asaluminum, copper, brass, silver, zinc, gold, pyrolytic graphite,bismuth, graphene, or carbon-nanotubes. In some examples, ferromagneticcombinations of materials, such as copper-iron, nickel-iron, lead-iron,brass-iron, silver-iron, zinc-iron, gold-iron, bismuth-iron,aluminum-iron, pyrolytic graphite-iron, graphene-iron,carbon-nanotubes-iron, or Alinco (aluminum-nickel-cobalt) alloys can beused as a flux barrier, in many cases with an electric conductivityhigher than ferromagnetic material (e.g., iron) making up the rotorpoles. In some cases, the FPFC, e.g., made of copper-iron, has aneffective magnetic permeability lower than the ferromagnetic material.In some cases, the FPFC, e.g., made of nickel-iron, has an effectivemagnetic permeability higher than the ferromagnetic material.

In some implementations, the first conductive loop 2102, the secondconductive loop 2104, or both, each have a respective substantiallyuniform inductance, particularly in the radial direction. In someimplementations, the first conductive loop 2102 can have a differentinductance than the second conductive loop 2104. In someimplementations, the first conductive loop 2102 can have substantiallythe same inductance as the second loop 2104 within standardmanufacturing tolerances. In some implementations, the individualconductors within both the first loop 2102 and the second loop 2104 havea small enough cross-sectional area to allow for full skin effectpenetration for a drive frequency. This arrangement allows for fluxpinning during operation of the motor 2200. More details on flux pinningare described throughout this disclosure.

A number of implementations using passive FPFCs have been described.While described as individual implementations, features of eachimplementation can be mixed and matched with one another withoutdeparting from this disclosure. For example, the first conductive loop2102, the second conductive loop 2104, or both, can be made of shortedlitz wire. In addition, other passive components, such as capacitors,resistors, or inductors, can be added in parallel or series with thevarious implementations described herein.

Example Radial-Gap Motors with Rectified FPFCs

This section primarily describes implementations relating to radial-gapmotors using rectified FPFCs. In the context of this disclosure, a“rectified” FPFC is an FPFC that that includes a rectifier connectingtwo ends of a conductor fully encircling at least one pole on a rotor.In the various implementations described herein, both internal rotorsand external rotors are described. While individual implementations maybe illustrated as either using an internal or an external rotor, it isnoted that aspects of the implementations described herein areapplicable to both internal rotors and external rotors regardless if theindividual implementation described.

FIGS. 23A-23C are views of an example rectified FPFC 2300 that can beused with aspects of this disclosure. FIG. 24A is a perspective view ofa portion of an electric motor 2400 using the rectified FPFC 2300illustrated in FIGS. 23A-23C. FIG. 24B is a planar view of a portion ofthe electric motor 2400 using the rectified FPFC 2300 illustrated inFIGS. 23A-23C. FIG. 24C is a planar cross-sectional view of a portion ofthe electric motor 2400 using the rectified FPFC 2300 illustrated inFIGS. 23A-23C. FIG. 24D is a perspective cross-sectional view of aportion of the electric motor 2400 using the rectified FPFC 2300illustrated in FIGS. 23A-23C. The electric motor 2400 is substantiallysimilar to the electric motor 500 with the exception of any differencesdescribed herein.

The FPFC 2300 has a similar geometry as the FPFC 400 illustrated inFIGS. 4A-4C; however, a rectifier 2306 has been added within theconductive loop 2302 to maintain a direction of current flow within theconductive loop. That is, the conductive loop 2302 includes a rectifier2306 in series with two ends of the conductive loop 2302. In someimplementations, the rectifier can include a diode. Several types ofdiode can be used, for example, a p-n junction diode, a gas diode, aZener, or a Schottky diode. In some implementations, when a Schottkydiode is used, the Schottky diode can be a silicon carbide diode. Diodeselection is a function of a variety of factors, including voltage drop,reverse voltage breakdown, and recovery time. Different diodes may beused depending on the desired operating conditions. While several typesof diodes have been listed, other diodes can be used without departingfrom this disclosure. In general, the directionality of each diode orthe winding direction of each FPFC alternates depending upon thepolarity of each rotor pole.

FIGS. 25A-25C are views of an example rectified FPFC 2500 that can beused with aspects of this disclosure. FIG. 26A is a perspective view ofa portion of an electric motor 2600 using the rectified FPFC 2500illustrated in FIGS. 25A-25C. FIG. 26B is a planar view of a portion ofthe electric motor 2600 using the rectified FPFC 2500 illustrated inFIGS. 25A-25C. FIG. 26C is a planar cross-sectional view of a portion ofthe electric motor 2600 using the rectified FPFC 2500 illustrated inFIGS. 25A-25C. FIG. 26D is a perspective cross-sectional view of aportion of the electric motor 2600 using the rectified FPFC 2500illustrated in FIGS. 25A-25C. The electric motor 2400 is substantiallysimilar to the electric motor 900 with the exception of any differencesdescribed herein. The FPFC 2500 is substantially similar to the FPFC 800previously illustrated in FIGS. 8A-8C with the exception of the additionof the rectifier 2306 that has been added to the conductive loop 2502.The rectifier 2306 functions as previously described.

FIGS. 27A-27C are views of an example rectified FPFC 2700 that can beused with aspects of this disclosure. FIG. 28A is a perspective view ofa portion of an electric motor 2800 using the rectified FPFC 2700illustrated in FIGS. 27A-27C. FIG. 28B is a planar view of a portion ofthe electric motor using the rectified FPFC 2700 illustrated in FIGS.27A-27C.

FIG. 28C is a planar cross-sectional view of a portion of the electricmotor 2800 using the rectified FPFC 2700 illustrated in FIGS. 27A-27C.FIG. 28D is a perspective cross-sectional view of a portion of theelectric motor 2800 using the rectified FPFC 2700 illustrated in FIGS.27A-27C. The electric motor 2600 is substantially similar to theelectric motor 700 with the exception of any differences describedherein. The FPFC 2700 is substantially similar to the

FPFC 600 previously illustrated in FIGS. 8A-8C with the exception of theaddition of the rectifier 2306 that has been added to the conductiveloop 2702. The rectifier 2306 functions as previously described.

FIGS. 29A-29C are views of an example rectified FPFC 2900 that can beused with aspects of this disclosure. FIG. 30A is a perspective view ofa portion of an electric motor 3000 using the rectified FPFC 2900illustrated in FIGS. 29A-29C. FIG. 30B is a planar view of a portion ofthe electric motor 3000 using the rectified FPFC 2900 illustrated inFIGS. 29A-29C. FIG. 30C is a planar cross-sectional view of a portion ofthe electric motor 3000 using the rectified FPFC 2900 illustrated inFIGS. 29A-29C. The electric motor 3000 is substantially similar to theelectric motor 1500 with the exception of any differences describedherein. The FPFC 2900 is substantially similar to the FPFC 1400previously illustrated in FIGS. 14A-14C with the exception of theaddition of the rectifier 2306 that has been added to the conductiveloop 2902. The rectifier 2306 functions as previously described.

FIG. 31A is a perspective view of an electric motor with an examplerectified FPFC 3101 mounted behind a permanent magnet 3120 on a rotor3108. FIG. 31B is a planar view of a portion of the electric motor 3100illustrated in FIG. 31A. FIG. 31C is a planar cross-sectional view of aportion of the electric motor 3100 illustrated in FIG. 31A. The electricmotor 3100 is substantially similar to the electric motor 1700 with theexception of any differences described herein. The FPFC 3101 issubstantially similar to the FPFC 1701 previously illustrated in FIGS.17A-17D with the exception of the addition of the rectifier 2306 thathas been added to the conductive loop. The rectifier 2306 functions aspreviously described.

FIG. 32A-32C are views of an example rectified FPFC 3200 that can beused with aspects of this disclosure. FIG. 33A is a perspective view ofa portion of an electric motor 3300 using the rectified FPFC 3200illustrated in FIGS. 32A-32C. FIG. 33B is a planar view of a portion ofthe electric motor 3300 using the rectified FPFC 3200 illustrated inFIGS. 32A-32C. FIG. 33C is a planar cross-sectional view of a portion ofthe electric motor 3300 using the rectified FPFC 3200 illustrated inFIGS. 32A-32C. FIG. 33D is a perspective cross-sectional view of aportion of the electric motor 3300 using the rectified FPFC 3200illustrated in FIGS. 32A-32C. The electric motor 3300 is substantiallysimilar to the electric motor 2200 with the exception of any differencesdescribed herein. The FPFC 3200 is substantially similar to the FPFC2100 previously illustrated in FIGS. 21A-21C with the exception of theaddition a first rectifier 2306a on the first conductive loop 3202 and asecond rectifier 2306b on the second conductive loop 3204. Therectifiers 2306a and 2306b are substantially the same as the rectifier2306 that has previously been described.

A number of implementations using rectified FPFCs have been described.While described as individual implementations, features of eachimplementation can be mixed and matched with one another withoutdeparting from this disclosure. For example, the first conductive loop3202, the second conductive loop 3204, or both, can be made of shortedlitz wire. In addition, other passive components, such as capacitors,resistors, or inductors, can be added in parallel or series with thevarious implementations described herein. For example, in someimplementations, a discrete capacitor (not shown) can be added to any ofthe rectified FPFCs described herein. The discrete capacitor can bewired in parallel or in series with any of the rectifiers describedherein. The addition of such a capacitor allows for tuning the FPFC tobe responsive to specified frequencies.

Example of Radial-Gap Motors with Active FPFCs

This section primarily describes implementations relating to radial-gapmotors using active FPFCs. In the context of this disclosure, an“active” FPFC is an FPFC that that includes any logic circuit, such as atransistor, connecting two ends of a conductor fully encircling at leastone pole on a rotor. In the various implementations described herein,both internal rotors and external rotors are described. While individualimplementations may be illustrated as either using an internal or anexternal rotor, it is noted that aspects of the implementationsdescribed herein are applicable to both internal rotors and externalrotors regardless if the individual implementation described.

FIGS. 34A-34C are views of an example active FPFC 3400 that can be usedwith aspects of this disclosure. FIG. 35A is a perspective view of aportion of an electric motor 3500 using the active FPFC 3400 illustratedin FIGS. 34A-34C. FIG. 35B is a planar view of a portion of the electricmotor 3300 using the active FPFC 3400 illustrated in FIGS. 34A-34C. FIG.35C is a planar cross-sectional view of a portion of the electric motor3500 using the active FPFC 3400 illustrated in FIGS. 34A-34C. FIG. 35Dis a perspective cross-sectional view of a portion of the electric motor3500 using the active FPFC 3400 illustrated in FIGS. 34A-34C. FIG. 35Eis a perspective view of the example motor 3500 using the active FPFC3400 illustrated in FIGS. 34A-34C. FIG. 35F is a longitudinalcross-sectional view of the example motor 3500 illustrated in FIG. 35E.FIG. 35G is a perspective cross-sectional view of the example motor 3500illustrated in FIG. 35E. The motor 3500 is substantially similar tomotor 500 previously described in FIGS. 5A-5D with the exception of anydifferences described herein. The active FPFC 3400 is substantiallysimilar to the passive FPFC 1400 with the exception of any differencesdescribed herein.

The FPFC 3400 includes a logic circuit 3406 in series with two ends ofthe conductive loop 3402. The logic circuit 3406 can includes atransistor, such as a field effect transistor, a dual gate field effecttransistor, or a bipolar junction transistor.

As illustrated, the logic circuit 3406 includes a transistor with asource 3408 and a drain 3410 defined by the short-circuited FPFC 3400. Agate 3412 of the transistor is connected to a slip ring 3520 thatprovides control signals. In some implementations, the leads, thetransistor, or both may be embedded in a printed circuit board (PCB)wherein the FPFC and slip ring 3520 or other control mechanism areconnected to. There are three slip rings 3521 (one shown) with threeleads 3522, one for each phase. The slip ring 3521 is grounded to therotor with a fourth slip ring 3524 as shown in FIGS. 35F-35G. The drain3410 on the transistor is also shown as grounded to the rotor 3508. Theleads 3522 coming out of the slip ring on the rotor shaft would becoupled to a controller, such as controller 130 (FIG. 2 ).

The additions of a logic circuit 3406 allows for the FPFC 3400 to beessentially “turned-off” during operation. This can be beneficial inhigh-speed, low load conditions, such as coasting. In someimplementations of active FPFCs, switches in active rectifiers may beimplemented such that, when in an unpowered state, the switches actpassively. For example, in some implementations a bipolar junctiontransistor rectifies current across two terminals in the absence ofactive control. Therefore, upon motor start-up, the active rectifieracts as a passive rectifier until active control is available.

While primarily illustrated and described as being wired to a controllerthrough conductive leads 3522, other communication mediums can be usedto send a control signal to the control circuit, for example, by lightsensitive diodes, capacitively coupled, or inductively coupledmechanisms, or by other wireless communication mediums.

Alternative Motors Using FPFCs

This section primarily describes implementations relating alternativeelectric machines, such as linear motors, axial gap motors, and toradial-gap motors with distributed windings, although descriptionsherein can apply to other implementations of radial or salient machines(e.g., concentrated wound, fractional slot, or radial machines).

Axial-Gap Motors with FPFCs

FIG. 36A is a perspective view of an example axial-gap motor 3600 thatcan be used with aspects of this disclosure. FIG. 36B is a side view ofthe example axial gap motor 3600 illustrated in FIG. 36A. FIG. 36C is aperspective view of the rotor 3608 used in the motor 3600 illustrated inFIG. 36A. FIG. 36D is a perspective view of the stator 3602 used in themotor 3600 illustrated in FIG. 36A.

The electric machine 3600 includes a stator 3602 defining multiplestator poles 3604 with associated electrical windings 3606. Asillustrated, the stator poles 3604 are shaped as circular sectors;however, other shapes can be used without departing from thisdisclosure. A rotor 3608 includes multiple rotor poles 3610. Similar tothe stator, the rotor poles 3610 are shaped as circular sectors;however, other shapes can be used without departing from thisdisclosure. While the present implementation has stator poles 3604shaped similarly to the rotor poles 3610, the stator poles 3604 androtor poles 3610 can be different from one another without departingfrom this disclosure. The rotor 3608 is movable with respect to thestator 3620. In this case, the rotor 3608 is arranged to rotate adjacentthe stator 3602. The rotor 3608 and the stator 3602 together define anominal gap 3612 between the stator poles 3604 and the rotor poles 3610.In this case, the nominal gap 3612 is an axial gap. The rotor poles 3610include a magnetically permeable pole material, such as iron. The rotor3608 also includes a series of frequency programmable flux channels(FPFCs) 3601. Each FPFC 3601 includes a conductive loop 3603 thatsurrounds or encircles an associated rotor pole 3610. In the illustratedimplementation, each rotor pole 3610 is encircled. The stator 3602 andthe rotor 368 are arranged such that the electrical windings 3606 in thestator 3602 induce an excitement current within the FPFCs 3601.

The rotor 3608 can be made of a magnetically permeable material, such asiron. In some implantation, the rotor 3608 can be made-up of rotorlaminations to reduce eddy currents within the back-iron of the rotor3608. Similarly, the stator 3602 can be made-up of stator laminations toreduce eddy currents within the back iron of the stator 3602. In someimplementations, the poles 3610 of the rotor 3608 include a materialwith a non-zero remanence. To retain each FPFC 3601 to their respectiverotor poles 3610, various fasteners, adhesives, or resins can be used.In some implementations, The FPFCs 3601 are retained with a friction orinterference fit.

As illustrated, the rotor 3608 includes no permanent magnets; however,permanent magnetic material can be used in the stator 3602, the rotor3608, or both without departing from this disclosure.

Similarly to previously described implementations, the FPFCs 3601include at least one conductive loop 3603 that has at least one turn ofshorted conductive material. That is, the conductive material fullyencircles a rotor pole 3610 and shorts itself to form a loop. In someimplementations, the conductive loop 3603 includes material moreconductive than a rotor core material. In some implementations, theconductive loop 3603 includes material less magnetically permeable thana rotor core material. Similar to the radial-gap implementations, theFPFCs 3601 have a substantially uniform inductance, particularly in aradial direction.

Such a criteria allows for full skin effect penetration of each FPFC3601 at a specified drive frequency. Conductor geometry, such asthickness of individual conductors within the conductive loop, isconsidered when designing the FPFCs 3601. In some implementations, drivefrequencies can extend between 0 hertz and 20 hertz. In someimplementations, drive frequencies can range between 100 hertz and 2000hertz. In some implementations, drive frequencies can extend between2,000 hertz and 15,000 hertz. As illustrated, the FPFCs 3601 arerectified FPFCs that include a rectifier 2306. While illustrated asusing rectified FPFCs, passive or active FPFCs can be used withoutdeparting from this disclosure.

Distributed Windings

FIG. 37A is a perspective view of an example electric motor 3700 withdistributed stator windings 3706 that can be used with aspects of thisdisclosure. FIG. 37B is a side view of the example electric motor 3700illustrated in FIG. 37A. FIG. 37C is a schematic view of the stator 3702in the electric motor 3700 illustrated in FIG. 37A. FIG. 37D is a planarcross-sectional view of the example motor 3700 illustrated in FIG. 37A.FIG. 37E is a perspective cross-sectional view of the example motor 3700illustrated in FIG. 37A. FIGS. 38A-38B are perspective and planar viewsof an example motor 3800 with distributed stator windings 3806 that canbe used with aspects of this disclosure.

Previous implementations described within this disclosure related torotors with salient poles and stators with salient poles. In someimplementations, a stator with distributes stator poles can be used. Insuch an implementation, the stator windings overlap one-another. Detailsabout how such an implantation is controlled, and any differences thatcan exist between controlling a motor with salient stator windingsversus distributes windings, are explained in greater detail later inthis disclosure. While distributed stator windings can be used withoutdeparting from this disclosure, the rotor poles and their associatedFPFCs are salient and non-overlapping in all implementations describedwithin. In some implementations, FPFCs within the same phase may beshorted to one another without departing from this disclosure. Such anarrangement is still considered non-distributed rotor poles.

Linear Motors with Frequency Programmable Flux Channels

FIG. 39A is a perspective view of an example linear motor 3900 withrectified FPFCs on the “rotor” 3908 (the passive magnetic section). FIG.39B is a longitudinal side view of the example linear motor 3900illustrated in FIG. 39A. FIG. 39C is a longitudinal cross-sectional viewof the example linear motor 3900 illustrated in FIG. 39A. FIG. 39D is aperspective view of the stator 3902 (the active magnetic section) of theexample linear motor 3900 illustrated in FIG. 39A. FIG. 39E is aperspective view of the “rotor” 3908 of the example linear motor 3900illustrated in FIG. 39A.

The electric machine 3900 includes a stator 3902 defining multiplestator poles 3904 with associated electrical windings 3906. A rotor 3908includes multiple rotor poles 3910. While the present implementation hasstator poles 3904 shaped similarly to the rotor poles 3910, the statorpoles 3904 and rotor poles 3910 can be different from one anotherwithout departing from this disclosure. As illustrated, the stator 3902is movable with respect to the rotor 3908. The rotor 3908 can act as apassive magnetic track that the active magnetic stator 3902 travelsacross. The rotor 3908 and the stator 3902 together define a nominal gap3912 between the stator poles 3904 and the rotor poles 3910. In thiscase, the nominal gap 3912 is a lateral gap. The rotor poles 3910include a magnetically permeable pole material, such as iron. The rotor3908 also includes a series of frequency programmable flux channels(FPFCs) 3901. Each FPFC 3901 includes a conductive loop 3903 thatsurrounds or encircles an associated rotor pole 3910. In the illustratedimplementation, every other rotor pole 3910 is encircled. The stator3902 and the rotor 3908 are arranged such that the electrical windings3906 in the stator 3902 induce an excitement current within the FPFCs3901.

The rotor 3908 can be made of a magnetically permeable material, such asiron. In some implantation, the rotor 3908 can be made-up of rotorlaminations 3914 to reduce eddy currents within the back-iron of therotor 3908. Similarly, the stator 3902 can be made-up of statorlaminations 3916 to reduce eddy currents within the back iron of thestator 3902. In some implementations, the poles 3910 of the rotor 3908include a material with a non-zero remanence. To retain each FPFC 3901to their respective rotor poles 3910, various fasteners, adhesives, orresins can be used. In some implementations, The FPFCs 3901 are retainedwith a friction or interference fit.

As illustrated, the rotor 3908 includes no permanent magnets; however,permanent magnetic material can be used in the stator 3902, the rotor3908, or both without departing from this disclosure.

Similarly to previously described implementations, the FPFCs 3901include at least one conductive loop 3903 that has at least one turn ofshorted conductive material. That is, the conductive material fullyencircles a rotor pole 3910 and shorts itself to form a loop. In someimplementations, the conductive loop 3903 includes material moreconductive than a rotor core material. In some implementations, theconductive loop 3903 includes material less magnetically permeable thana rotor core material. Similar to the radial-gap implementations, theFPFCs 3901 have a substantially uniform inductance, particularly in aradial direction. Such a criteria allows for full skin effectpenetration of each FPFC 3901 at a specified drive frequency. Conductorgeometry, such as thickness of individual conductors within theconductive loop, is considered when designing the FPFCs 3901. In someimplementations, drive frequencies can extend between 0 hertz and 20hertz. In some implementations, drive frequencies can range between 100hertz and 2000 hertz. In some implementations, drive frequencies canextend between 2,000 hertz and 15,000 hertz. As illustrated, the FPFCs3901 are rectified FPFCs that include a rectifier 2306.

FIG. 40A is a perspective view of an example linear motor 4000 withrectified FPFCs on the “rotor” 4008 and the stator 4002. FIG. 40B is alongitudinal side view of the example linear motor 4000 illustrated inFIG. 40A. FIG. 40C is a longitudinal cross-sectional view of the examplelinear motor 4000 illustrated in FIG. 40A. FIG. 40D is a perspectiveview of the stator 4002 of the example linear motor 4000 illustrated inFIG. 40A. The linear motor 4000 is substantially similar to the linearmotor 3900 with the exception of any differences described herein.

The stator 4002 includes two rectified FPFCs 4001 on the stator poles4004. The addition of the two rectified FPFCs per stator pole 4004allows for flux pinning within the stator poles 4004. That is, the fluxis topologically constrained to a desired area of the stator pole. Whileillustrated as using rectified FPFCs, passive or active FPFCs can beused without departing from this disclosure.

Operation of Motors with Frequency Programmable Flux Channels

This section describes general motor concepts that are applicable toelectric motors with FPFCs. While described primarily in the context ofrotating electric motors, the concepts described herein are applicableto other motors as well. In some instances, the concepts describedherein are applicable to motors without FPFCs.

A magnetic material can be classified as “soft” or “hard” based upon itscoercivity. Traditionally, synchronous motors don't have magnetizingcurrent to magnetize a material so magnets have to be magnetized at thefactory or prior to installation. To that effect, if the magneticmaterial demagnetizes under operation (e.g., because the stator isputting too much of a load on it or due to thermal effects generatedthroughout operation) the magnet can be damaged, or the motor can berendered inoperable entirely. Thus, “hard” materials are often used inpermanent magnet synchronous machines. Moreover, regardless of magneticmaterial, sufficiently large quantities of such magnetic material aretypically used to ensure a given field strength (B) and coercivity (H).FIG. 41A is a hysteresis diagram of a “soft” magnetic material and FIG.41B is a hysteresis diagram of a “hard” magnetic material. The coerciveforce for the “hard” magnetic material is larger than that of “soft”magnetic material. Referring back to FIGS. 3A-3D, the inverted pulses306 can magnetically harden (or stiffen) the rotor poles 308 thatinclude an FPFC 310. The FPFC itself can also assist in supporting theflux of a given magnetic material, or magnetically permeable material,throughout operation (e.g., under sinusoidal or square-wave control).

FIG. 42 is a schematic diagram of an electric motor 4300 with alignmentsbetween the rotor 4308 and the stator marked 4301. Position D is definedas opposite stator & rotor poles being aligned, Q & Q′ as fullyunaligned (approaching similar poles and opposite poles respectively),and D′ as similar stator and rotor poles aligned. Motor components andcontrols are sometimes discussed in reference to a D-axis 4302 andQ-axis 4304 of a motor rotor and/or stator. In such a transformedsystem, the direct axis, or D-axis 4302, in a motor may be defined asthe center line of a pole perpendicular to the air gap 4306, and may beapplied to either a stator pole 4308 or rotor pole 4312. A rotor may becharacterized with a D-axis 4302 for each pole as viewed in thesynchronous reference frame. In a motor with salient rotor poles andFPFCs, the D-axis 4302 is the center point of the resultant magneticcenter of a pole with an FPFC regardless of whether the FPFC isconcentrated to a single, large slot or spread across multiple, smallerslots. Stator poles can be similarly characterized.

The Q-axis 4304 is normal to the D-axis 4302 within the magneticreference frame. In some implementations, the Q-axis 4304 iselectrically normal to the D-axis 4302, and both lie in a plane in whichthe rotor rotates. In general, forces along the Q-axis 4304 generate anelectromotive force, such as torque. Topologically, the Q-axis 4304 of arotor or a stator is typically located directly between two poles.

In the D-Q reference frame, a current phasor angle is the relative angleof a rotor D-axis 4302 to the magnetic center of the stator. A positivecurrent phasor angle indicates that the magnetic center of the stator isahead of the rotor pole in a direction of motion. Such a situationresults in the magnetic center of the stator “pulling” the rotor poletowards the magnetic center of the stator. Similarly, a negative currentangle indicates that the magnetic center of the stator is behind therotor pole. Such a situation “pulls” the rotor pole in the oppositedirection. Such a negative current phasor angle can be used in brakingsituations. In some implementations, a current phasor angle of greaterthan 90° can be used. Such a large phasor current angle can “push” anadjacent pole in the direction of motion. Similarly, a current phasorangle of less than −90° can be used to “push” an adjacent pole in anopposite direction, such as during braking operations. Converting thecurrent phasor angle between the stationary and synchronous referenceframes can be done using the following equation:

θ_(e)=(P/2)θ_(m),   (1)

where θ_(e) is the current phasor angle in the synchronous referenceframe, P is the number of stator poles, and θ_(m) is a current phasorangle in the stationary reference frame. Regardless of the currentphasor angle, it can be broken down into a D-axis component and a Q-axiscomponent. In general, for the motors and generators described herein,the D-axis component acts to “charge” or modulate the field within arotor pole and FPFC while the Q-axis component acts to impart a force ortorque onto the rotor pole.

FIG. 43A is a graph showing torque of the rotor relative to the positionof the rotor relative to the stator. In some implementations, especiallyin rotors with high saliency, peak toque occurs between the D and Qpositions in the synchronous reference frame (e.g., due to itsreluctance component). In other implementations, peak torque occursbetween Q and D′ positions. In instances where a permanent magnet motoris used, peak torque operation can cause demagnetization at high loadand require field weakening at high speed. Weaker magnets can be used tothe detriment of size/weight and/or torque production. To increase themagnetic current capabilities without risk of demagnetization FPFC's areused. FIG. 43B is a graph showing the current flow within an FPFC duringrotation of the rotor. The negative current portion 4310 is present inthe simple FPFC implementations, but is eliminated with rectified oractive FPFC implementations. At lower torques, FPFC current can beallowed to reduce lowering cogging (resistive) torque and eliminatingthe need for active flux weakening of stronger permanent magnets. Anadvantage of FPFCs is that they can be flux weakened or strengthened(e.g., current decrease or increase within the FPFC and flux within therotor pole itself) through control mechanisms, for instance, bymodifying the current phasor angle of the synchronous excitation fromthe stator. There is no need for a secondary control system oradditional commutation hardware such as in a wound rotor synchronousmotor (e.g., to control the stator field).

Control schemes for the FPFC implementations included herein do notnecessarily require additional stator-to-rotor coupling elements;rather, in some implementations, excitations are transmitted using thestator windings and FPFCs along with the rotor. This can help reduce atotal number of components, increase performance (e,g., eliminatingohmic losses of brushes), eliminate physical contacts and wearcomponents, reduce package size, and provide control flexibilitycompared to schemes that incorporate special detectors, sensors, wiredor wireless connections, or brushes to transmit signals from stator torotor.

In electric machine design, the stator and rotor are often coupled toenable power transfer and/or field modulation during operation.Couplings may be classified as direct coupling or indirect coupling.Direct coupling occurs between the stator and rotor along the primaryoperating air-gap. Indirect coupling occurs along a secondary interfaceaway from the primary operating air-gap.

Direct couplings are typically characterized as inductively coupled, forexample, a squirrel cage induction rotor is considered to be directlycoupled to the stator. While direct coupling is common and easilycontrolled in asynchronous machine, direct coupling with synchronousmachines can be difficult for reasons described throughout thisdisclosure and are difficult to control.

Indirect couplings operate along a secondary coupling and may be radialoriented or axially oriented, and may communicate via electricalcontacts, inductive couplings along a separate air-gap, capacitivelycoupled, or optically coupled. While secondary coupling may be used fora variety of functions to improve the efficiency and/or overallcontrollability of an electric machine, additional components are oftenrequired that can increase the weight, complexity, failure frequency,and costs (both operating and capital costs) of machines that takeadvantage of such systems.

Motors and generators described in this disclosure are primarilyenergetically isolated (within standard electromagnetic shieldingtolerances) where they use direct coupling to transmit power and signalsbetween the stator and the rotor without the necessity of an indirect orsecondary coupling. Direct coupling can control torque, speed, controlflux of the rotor. The electric machines described herein include directcoupling between the rotor 404 and the stator 402 for both torque,speed, flux and signal coupling and control.

A frequency and harmonic independence can be observed in someimplementations between the signal emitted by the stator, and the baseoperating frequency that determines rotor speed. In someimplementations, the subject matter described herein is able to providea constant excitation frequency to the rotor regardless of rotor speed,and even use the modulation of stator excitation such as frequencymodulation as discussed herein under constant or dynamic speedconditions. Control of FPFCs does not rely on harmonic relationshipsbetween the stator and rotor, or base frequency and higher orderharmonics, enabling the FPFCs in the rotor to be designed, andcontrolled, around specific parameters (e.g., control and material).Various controls schemes for FPFCs been discussed throughout thisdisclosure and are explored further herein.

In some instances, FPFCs may need to be, or benefit from being, chargedwhen located on position D, or transitioning from position D to positionQ. Charging may mean inducing current in the FPFC itself ortransferring, increasing, or storing magnetic flux in the rotor, each ofwhich may involve some power transfer from the stator to the rotor. Sucha task can be accomplished in a variety of ways, for example, bymodulating a current phasor angle of stator excitation (e.g., advancingor retarding the current angle of stator excitation as appropriate),increasing a frequency of change in the stator excitation current phasorangle, increasing amplitude of excitation current in the stator (or anyof the stator's resultant signal components), or any combinationthereof. In some instances, the FPFCs may be weakened (e.g., decreasingthe level of current or magnetic flux present in the FPFC and/or rotor),for example, by operating on or near position D′ (e.g., by transitioningfrom position Q to position D′, or form position D′ to Q′). Such a taskcan be accomplished in a variety of ways, such as modulating the currentphasor angle (e.g., advancing or retarding the current angle of statorexcitation as appropriate), decreasing the frequency of statorexcitation current angle phasor change, decreasing the amplitude ofexcitation current in the stator, or any combination thereofAlternatively or in addition too, field weakening can be accomplishedthrough a passive loss of FPFC current via ohmic losses.

As previously mentioned, active field weakening of the FPFCs can beachieved by operating in D′ or by replacing the using an active FPFC.Such implementations include a logic circuit, such as a transistor, thatmay be inductively or capacitively coupled and controlled,conventionally through slip rings or a commutator, or wirelessly whichmight include a means of optional control, e.g., a light emitting diode,photo sensor or primary control. Reversing rectification with the logiccircuit causes a rapid reduction in FPFC current via the inductivecoupling with the stator excitations. Leaving the gate 3412 (FIGS.34A-35G) open will not allow current in the FPFCs to build and thereforeno reactive current can be generated.

For any of implementations described throughout this disclosure, if apermanent magnetic material is used within the pole, the FPFC circuitwinding and diode polarity can be arranged to provide various outputs.For instance, in some implementations the rectification can beconstructive, such that they are constructive to the polarity ormagnetomotive force (MMF) of the material. This provides magneticshielding against unwanted fields and harmonics; rotor magnetic fieldaugmentation, where the remnant magnetic field of the rotor pole isincreased from a residual value during operation (e.g., amplificationusing the coils); and magnetic flux charging where a material ismagnetized to a remnant field (e.g., fluxing of a material). In otherimplementations, the rectification can be deconstructive, such that theycan decrement a magnetic field (e.g., field weaken). In someimplementations with active FPFCs, the active FPFCs would allow forbi-directional rectification and the selective constructive ordeconstructive rectification using logic gates and associated control.

All of the concepts and operations described herein can be applied toelectric machines with wound rotors or permanent magnet assisted woundrotors. Specifics of increasing or decreasing/maintain charging in FPFCsdependent on speed, torque and other operating conditions. For example,high torque demand and low speed require more charging. For example,high speed low torque may demand the lowest average FPFC currentpossible while maintaining torque requirements. It should be noted thatrotor speed is not intended to change when stator excitation advanced orretarded. Torque and speed remain constant until a control requestdictates change.

In distributed stator pole implementations, to maintain substantiallyzero torque ripple (in some implementations, equal to or less than 1%,in other implementations between 0-2%), the stator can be excited oramplified in the D position where the excitation alignment, or currentphasor angle, works to augment the rotor field. The current phasor angle(and resultant magnetic field) can then be rotated to substantially nearthe peak torque position (or whatever the controller set point is) whilemaintaining synchronous timing. The excitation wave can periodically beshifted to the peak charge position to field strengthen the FPFC. Inimplementations where a rectified FPFC is used, the period of theexcitation wave may not be equal. In such a situation, the current canbe increased during the charge phase to compensate for flux leakage andreluctance torque. Three-phase excitation timing can be timed to keepthe excitation wave leading the rotor or in the synchronous referenceframe

While steady state operation has been described, different drivewaveforms may be needed for locked rotor (start-up) conditions. FIG. 44Ais a set of graphs illustrating drive wave forms 4400 a, 4400 b and 4400c during a locked rotor condition. Each waveform, 4400 a, 4400 b and4400 c, is associated with a different phase of a 3-phase motor. Duringnormal start-up of a synchronous machine, direct current is sent to eachphase to have the rotor begin to rotate in the desired direction. Withmachines utilizing FPFCs, a periodic pulse of inverted current is usedto charge the FPFCs until the rotor begins moving. This signal may rangefrom a pulsed to continuous sine wave as a function of the rotor speedas described elsewhere in this document where, at higher speeds, thepulse and charge cycles overlap as the mechanical timing reaches thepulse frequency. Therefore the waveform adopts a fundamental wave. Insome implementations, the quasi-direct current, or a transform thereof,is flowed for nine milliseconds, and the inverted direct current ispulsed for one millisecond. In some implementations, a ratio of durationof quasi-direct current to a duration of pulsing inverted current is 1:1to 100:1. In some implementations, the ratio of duration of quasi-directcurrent to a duration of pulsing inverted current is 5:1 to 15:1. Insome implementations, a ratio of duration of quasi-direct current to aduration of pulsing inverted current is 9:1. Regardless of the ratioused, once the rotor begins movement, the rotor can then be driven by analternating current flowing through each of the phases. Such atransition is illustrated in FIG. 44B. FIG. 44B is a graph illustratingthe transition from locked rotor condition to moving rotor condition.While the locked rotor conditions is illustrated as square waves and thedrive frequency is illustrated as sinusoidal waves, other wave forms canbe used for each operating condition without departing from thisdisclosure.

As previously described effects of FPFCs can vary under differentfrequencies. For example force can start to increase above a cutofffrequency, e.g., 10 hertz, and the increase between a lower frequency,e.g., 10 hertz, and a higher frequency, e.g., 10⁵ hertz, can be morethan one order of magnitude. At higher frequencies, an FPFC can exhibitstronger diamagnetic properties to concentrate the magnetic flux towardsthe rotor pole, which in turns increases the component of force alongthe motion direction.

The useful force can be also affected by operating conditions. Undersaturated conditions and at a high frequency, the FPFCs can exhibitstronger diamagnetic properties to concentrate the magnetic flux towardsthe rotor pole, compared to in unsaturated conditions. The useful forcecan keep increasing when the frequency increases. For example, at ahigher frequency, e.g., 10⁵ hertz, the horizontal force can increase twoorders of magnitude when a drive current increases from 10 Amp*turns(corresponding to an unsaturated operation condition) to 200 Amp*turns(corresponding to a saturated operation condition).

A number of teeth per pole can also have an effect on useful force. Anincrease in the number of teeth per pole can cause gradual increase inthe force. However, when a gap size becomes larger, e.g., at 1.0 mm, theforce may decrease when the number of teeth per pole increases.

The operation utilizes high-inductance and low-resistance FPFCs,resulting in a high reactance that is in phase with the magnetic field.As the magnetic field climbs through the primary coils and reluctanceteeth, the magnetic field is reflected through the shielded teeth andresults in high impedance to the magnetic field. This system can beoperated through an alternating magnetic signal only through 50% of dutycycle (e.g., from unaligned to aligned). Continuing throughout the dutycycle (e.g., from aligned to unaligned) can result in inverse torque. Insome implementations, an impedance matching or impedance network can beestablished.

A higher reactance FPFC can also enable a higher power factor systemthat can generate torque more efficiently compared to a conventionalmachine. The high reactance, high impedance FPFC design can preventsubstantially all of the magnetic flux from penetrating the FPFCthroughout the entire cycle of operation. In this way, the motor canbenefit from diamagnetic properties previously only experienced in superconducting motors at a broad range of temperatures (e.g., roomtemp-elevated temp). This can also be less sensitive to temp as comparedwith permanent magnet motors, which tend to demagnetize above a criticaltemperature.

The motors described above with FPFCs can be driven dynamically with asquare wave current. If it is driven dynamically, a square wave may beused at a relatively lower switching frequency than an equivalent sinewave to induce large reactance in the FPFC while pulsing at a relativelylow frequency (such as 50 hertz). This is due in part to the highproportion of harmonic values in a square wave as opposed to a sinewave. This also decreases switching losses required by a powerelectronic device due to high frequently required by pulse-widthmodulation (PWM) switching. In such operation, relatively thin (e.g.,0.127 mm) laminations can be used to decrease eddy current loss in coreiron and low gauge (e.g., 0.2 mm) or even Litz wire windings can beutilized in the primary coils to decrease skin effect losses in the corewindings.

The motors described throughout this disclosure can also benefit fromhigher winding efficiency of the coils. Whereas the typical slot fillratio of a winding is 30-40% of a given slot area, by utilizing castingtechniques to fill FPFCs in slots between adjacent poles the motor canutilize substantially all (e.g., 85-95%) of the slot volume for theFPFCs. This can decrease the amount of total wire necessary for theprimary winding of the motor, which can enable the primary winding touse less turns compared to a typical motor.

As noted above, filling the slots with FPFCs allows for the controlledconcentration of the magnetic flux in operation of the motor.Specifically, when the stator and rotor are disposed in an unalignedstate, significant internal electromagnetic reflection prevents themajority of magnetic communication from the opposing pole surfaces. Thisdiamagnetic shielding allows the field slots to effectively push therotor while the reluctance of the electromagnetic poles pull the rotor.This effect allows more energy per cycle to be produced from the systemand is similar to the effect permanent magnets can produce in certainconfigurations.

This effect provides a notably advantage over permanent magnets, whichmay be subject to demagnetization by high eddy currents. This effect maybe seen in a B-H curve examining coercivity of a permanent magnet. Inthe motors described throughout this disclosure, a high reactance FPFCcan approximate a permanent magnet in the opposite direction with aninfinite coercivity. Thus, the FPFC can reflect the imposed magneticfield to achieve magnetic field levels beyond what may be achieved intypical permanent magnet motors, which can increase torque density,power density, and efficiency by creating a larger back EMF. Moreover,whereas permanent magnets demagnetize at elevated temperatures aspreviously mentioned, FPFCs can be constructed of materials capable ofwithstanding temperatures over 100 degrees Fahrenheit hotter thantypical permanent magnets.

Moreover, where permanent magnets produce a constant magnetic field, theFPFCs exists dynamically in a transient state. This benefits bothefficiency and safety, as permanent magnet motors can result in denttorque, cogging torque, and braking torque, which can sometimes becatastrophic due to the EMF that can be produced whether or not power itutilized. The above motors can be controlled to effectively freewheelfor long periods of time, with losses only from the resistance of thebearings.

Further, unlike an IM having significant inductive load that generates acontinuous current, the current in each FPFC is allowed to go back tonear zero each cycle. The higher the operating frequency of the motor,the lower the necessary current is required in each FPFC to maintainreflection. Because the system is reactive, energy is either returnedelastically or translated into kinetic energy of the rotor in eachswitching cycle.

The FPFC slot filling can be tuned, both for a given application anddynamically during operation. Unlike air, the magnetic properties of thesystem can be tuned, both in amplitude of magnetomotive force (MMF) fora given position, and in frequency of the MMF. This allows for real timeadaptation by weakening or strengthening the magnetic flux properties ofthe system by changing the switching frequency of the motor. This canchange the back-EMF on the primary coil, which can allow the motor toachieve broader speed ranges than traditional motors. Traditional motorshave a fixed back-EMF based on a fixed saliency ratio, which is used tochange the magnitude of magnetic field. The motor can change themagnitude of the magnetic field, in addition to the activating frequencyof the motor's operation.

At higher speeds, the motor can operate as a reactive reluctance motor.In conventional SRM operation, peak voltage is applied at onset of theunaligned position of stator and rotor (or the stator-rotor teeth) andcurrent is rapidly increased until the stator and rotor (or thestator-rotor teeth) reach a point of alignment. At this point, a reversevoltage is applied and current then drops to zero. In a locked rotor(stall) condition in a conventional SRM, current is continuously appliedrather than pulsed. In a motor with FPFCs, during stall current can bepulsed through an active coil. Once pole switching frequency exceeds thecross-over frequency of the FPFCs during motor acceleration, each polemay be excited by a single pulse.

Example Process

Implementations of the present disclosure provide a method of driving anelectric motor. The electric motor can be the electric motor 102 of FIG.1 , and the method can be performed by a motor controller, e.g., themotor controller 107 of FIG. 1 or the controller 130 of FIG. 2 .

During operation, the motor controller applies a pulse of magnetizingcurrent over time to a stator coil of a stator pole when the stator poleis aligned with a rotor pole across a nominal gap. The magnetizingcurrent is configured to charge a magnetic field within the rotor polethrough induced direct coupling. Then, the motor controller applies aload current pulsed over time to the stator coil when rotor pole ispositioned between adjacent stator poles. The load current pulsesstiffen the magnetic field within the rotor pole. The pulsed loadcurrent include more pulses per increment of time than pulse themagnetizing current.

In some instances, the magnetizing current is applied as a single pulseof current over time. The single pulse of current can include ahalf-sine wave, a half-square wave, a half-trapezoidal wave, or anycombination thereof. Applying the magnetizing current strongly couplesthe rotor pole to the stator pole. In some instances, for instance whena rotor has a sufficient field strength, no magnetizing (or less)current is applied when compared to previous time steps.

In some instances, the pulsed load current is applied as a rotor rotatesfrom a first pole to a second pole. The multiple pulses of the pulsedload current can include half-sine waves, half-square waves,half-trapezoidal waves, full sine waves, full square waves, fulltrapezoidal waves, or any combination thereof. In some implementations,signals may have a DC offset. In some implementations, the multiplecurrent pulses are not a function of a rotor speed. For example, in someimplementations, the multiple current pulses are applied between five toten hertz. In some implementations, the multiple current pulses areapplied between 5-1000 hertz, 10-500 hertz, 50-350 hertz, or 100-200hertz.

In some implementations, the controller maintains a rotor flux within adesired range during peak load condition. For example, the desired rangecan vary within 50-100%. In another example, the desired range can varywithin 65-100%. In another example, the desired range can vary within80-100%.

As previously described, the motor controller can adjust a strength ofapparent magnetism within the permanent magnet channels, or any otherpermanent magnetic material within the rotor, by inducing a currentwithin the FPFCs.

The previously described operating parameters can be performed by thecontroller by operating a first switch to open and close in multiplecycles between a voltage source and the electrical winding associatedwith the first active pole. The first switch can be associated with thefirst active pole and conductively coupled to the first active pole. Thefirst switch can be the switch 134 of FIG. 2 or the power switch 200 ofFIG. 2A.

Example Cooling and Heat Mitigation

Electric motors can generate significant heat during operation andrequire cooling, especially during higher frequency operation. An activecooling system can be used to provide intermittent or continuous coolingof surface by circulating a fluid coolant through the motor. The coolingsystem can be the cooling system as described in pending patentapplication Ser. No. 62/675,207, filed on May 23, 2018 and entitled“Electric Motor,” the contents of which are expressly incorporatedherein by reference as if set forth in their entirety.

Also, if operating temperatures are depressed, the efficiency and powerof a FPFC can increase for a given frequency. Typically operatingconditions are −80° C. to 300° C. Coolant may be added to the motorsystem to further suppress the temperature and increase the diamagneticproperties of a FPFC.

A coolant may be any conventional fluid used for heat mitigation. Atoperating conditions, the coolant may be a low viscosity fluid in therange of 1 to 500 centipoise, such as water or motor oil to allow forboth high cooling efficiency and rotational dynamics. Coolant may alsoprovide the damping of vibration generated during operation, as well asproviding restorative force to harmonics that are generated at higherrotational speeds.

Active cooling may enable greater power density by providing a medium toabsorb heat from electrical coils and mechanical contact surfaces. Anactive lubrication system may be used to provide intermittent orcontinuous lubrication of surface by circulating a fluid lubricantthrough the motor. For example, a fluid pump may mechanically promote alubricant to flow from the fluid pump to the motor via fluid lines,where it may be discharged via directional nozzles to provide activelubrication and/or fluid cooling to specific locations within the motor.Fluid may then gravitationally collect in an oil pan at the base of themotor and flow via a return fluid line back to the pump forrecirculation. In this way, a motor rotor assembly may operate in acool, non-submerged environment. In addition, a portion of the lubricantmay pass through a heat exchanger to add or remove heat from thelubricant in order to modulate the temperature and/or viscosity of thelubricant to meet the specific needs of an application.

A coolant may be any conventional fluid used for heat mitigation. Atoperating conditions, the coolant may be a low viscosity fluid in therange of 1 to 500 centipoise, such as water or motor oil to allow forboth high cooling efficiency and rotational dynamics. Coolant may alsoprovide the dampening of vibration generated during operation, as wellas providing restorative force to harmonics that are generated at higherrotational speeds.

The motor may include a collection pan to gravitationally collect thecoolant discharged within the motor assembly and direct it toward areturn fluid line.

The coolant system may have a fluid pump that provides a pressuregradient to the coolant resulting in circulation through the fluidsystem. Such a pump may be a fixed displacement pump, such as a rotarypump, or a variable displacement pumps, such as a gear or piston pump.The pump may be operationally connected to a mechanical or electricalpower source and may be operated continuously or intermittently duringmotor operation. A wet sump active lubrication system may have a singlefluid pump operationally connected to a collection pan to circulate oilthrough fluid lines and within the cooled system. In this case, themajority of the oil supply is located in the collection pan.Alternatively, multiple fluid pumps may be operated in a dry sump activecoolant configuration where fluid from the collection pan iscontinuously pumped into a holding tank, preferably with a large heightrelative to its cross-sectional area, and a second pump may pump thefluid under a separate, controlled flow rate back to the motor tocomplete coolant circulation.

The coolant system may have one or more directional nozzles to directcoolant to specific locations within the motor assembly including, forexample, the stator poles.

Other Implementations

Any of the above-described motors can be controlled to generateelectrical energy from dynamic energy (such as for regenerativelybraking the motor). This may be accomplished by altering the timing ofthe excitation signal such that stator current is pulsed at the point ofminimum air gap (or even slightly lagging the point of minimum air gap)to generate forward EMF during expansion. In this manner, electricalcurrent can be generated and directed to storage in an associatedbattery while a deceleration torque is applied to the rotor to slow themotor, even though the motor is not mechanically back drivable by torqueapplied to the output shaft.

Any of the above-described motors can be controlled to generateelectrical energy from dynamic energy (such as for regenerativelybraking the motor). This may be accomplished by altering the timing ofthe compression wave such that stator current is pulsed at the point ofminimum air gap (or even slightly lagging the point of minimum air gap)to generate forward EMF during expansion. In this manner, electricalcurrent can be generated and directed to storage in an associatedbattery while a deceleration torque is applied to the rotor to slow themotor, even though the motor is not mechanically back-drivable by torqueapplied to the output shaft.

While a number of examples have been described for illustrationpurposes, the foregoing description is not intended to limit the scopeof the concepts described herein, which is defined by the scope of theappended claims. There are and will be other examples and modificationswithin the scope of the following claims. Other implementations andmodifications are within the scope of the following claims and have thebenefit of this disclosure. It is intended to embrace all suchimplementations and modifications and, accordingly, the abovedescription to be regarded as illustrative rather than in a restrictivesense. In some cases, the actions or methods recited in the claims canbe performed in a different order and still achieve desirable results.In addition, the processes depicted in the accompanying figures do notnecessarily require the particular order shown, or sequential order, toachieve desirable results, and various elements may be added, reordered,combined, omitted, or modified.

What is claimed is:
 1. A synchronous electric machine comprising: astator defining multiple distributed stator poles with associatedelectrical windings that overlap one another ; a rotor comprisingmultiple rotor poles, the rotor movable with respect to the stator anddefining, together with the stator, a nominal gap between the statorpoles and the rotor poles, the rotor poles comprising a magneticallypermeable pole material; and a plurality of frequency programmable fluxchannels (FPFCs), wherein current induced in the each FPFC generates amagnetic field configured to oppose an alternating magnetic fieldinduced between the stator and the rotor, thereby producing a repellingforce therebetween.
 2. The synchronous electric machine of claim 1,wherein the repelling force concentrates or redirects magnetic flux ofthe magnetic field substantially tangentially along a direction ofrelative motion between the rotor and the stator to increase a forceavailable to do work by the synchronous electric machine.
 3. Thesynchronous electric machine of claim 1, wherein the magnetic fieldconfigured to oppose an alternating magnetic field is a reflective orresistant magnetic field, such that each FPFC controllably attenuates achange in total magnetic flux of the synchronous electric machine duringoperation.
 4. The synchronous electric machine of claim 1, wherein eachrotor pole and associated FPFCs are salient and non-overlapping withrespect to other rotor poles and associated FPFCs.
 5. The synchronouselectric machine of claim 1, wherein the stator and the rotor arearranged such that the electrical windings in the stator induce anexcitement current within at least one of the FPFCs during start-up orwherein the stator and the rotor are arranged such that the electricalwindings in the stator magnetize at least one of the rotor poles duringstart-up.
 6. The synchronous electric machine of claim 1, wherein eachof the FPFCs do not overlap with an adjacent FPFC.
 7. The synchronouselectric machine of claim 1, wherein the conductive loop comprises asubstantially uniform inductance.
 8. The synchronous electric machine ofclaim 1, wherein the conductive loop comprises a rectifier in serieswith two ends of the conductive loop.
 9. The synchronous electricmachine of claim 1, wherein the conductive loop includes a discretecapacitor or a logic circuit in series with two ends of the conductiveloop configured to tune the FPFC to be responsive to specifiedfrequencies.
 10. The synchronous electric machine of claim 1, whereinthe conductive loop is a first conductive loop and the rotor pole is afirst rotor pole, and wherein each FPFC further comprises a secondconductive loop the associated rotor pole and an additional rotor poleadjacent the first rotor pole.
 11. The synchronous electric machine ofclaim 1, further comprising a controller configured to: apply a pulse ofmagnetizing current over time to a stator coil of a stator pole when thestator pole is aligned with a rotor pole across a nominal gap, whereinthe magnetizing current is configured to charge a magnetic field withinthe rotor pole through induced coupling; and apply a load current pulsedover time to the stator coil when rotor pole is positioned betweenadjacent stator poles, wherein the load current pulses stiffen themagnetic field within the rotor pole, and wherein the pulsed loadcurrent comprising more pulses per increment of time than pulse themagnetizing current.
 12. A motor control method comprising: applying apulse of magnetizing current over time to a stator coil of a stator polewhen the stator pole is aligned with a rotor pole across a nominal gap,the magnetizing current configured to charge a magnetic field within therotor pole through induced coupling; and applying a load current pulsedover time to the stator coil when rotor pole is positioned betweenadjacent stator poles, the load current pulses stiffening the magneticfield within the rotor pole, wherein the pulsed load current comprisingmore pulses per increment of time than pulse the magnetizing current.13. The motor control method of claim 12, further comprising controllingthe magnetizing current and the pulsed load current to change themagnetic properties of a motor including the rotor and the stator. 14.The motor control method of claim 12, wherein the magnetizing currentproduces a radial force vector relative to an axis of rotation of therotor and the pulsed load current produces a tangential force vectorrelative to the axis of rotation of the rotor.
 15. The motor controlmethod of claim 12, wherein applying a pulse of magnetizing current overtime and applying a load current pulsed over time are performedaccording to a ratio of duration of direct current to a duration ofpulsing inverted current selected to magnetically harden the rotor polein response to a sinusoidal drive frequency.
 16. The motor controlmethod of claim 15, wherein the ratio is one of 1:1, 100:1, 5:1, 15:1 or9:1.
 17. The motor control method of claim 12, wherein applying themagnetizing current is applied as a single pulse of current over time.18. The motor control method of claim 12, wherein applying the pulsedload current comprises applying multiple current pulses over time as arotor rotates from a first pole to a second pole comprising one ofhalf-sine waves, half-square waves, half-trapezoidal waves, full sinewaves, full square waves, or full trapezoidal waves.
 19. The motorcontrol method of claim 12, wherein the multiple current pulses are nota function of a rotor speed.
 20. The motor control method of claim 12,further comprising maintaining a rotor flux within a desired rangeduring peak load condition, and wherein the desired range varies within50-100%.